Imaging Markers Derived From MRI-Based Automated Kidney Segmentation—an Analysis of Data From the German National Cohort (NAKO Gesundheitsstudie)

BACKGROUND

Population-wide research on potential new imaging biomarkers of the kidney depends on accurate automated segmentation of the kidney and its compartments (cortex, medulla, and sinus).

METHODS

We developed a robust deep-learning framework for kidney (sub-)segmentation based on a hierarchical, three-dimensional convolutional neural network (CNN) that was optimized for multi-scale problems of combined localization and segmentation. We applied the CNN to abdominal magnetic resonance images from the population-based German National Cohort (NAKO) study.

RESULTS

There was good to excellent agreement between the model predictions and manual segmentations. The median values for the body-surface normalized total kidney, cortex, medulla, and sinus volumes of 9934 persons were 158, 115, 43, and 24 mL/m2. Distributions of these markers are provided both for the overall study population and for a subgroup of persons without kidney disease or any associated conditions. Multivariable adjusted regression analyses revealed that diabetes, male sex, and a higher estimated glomerular filtration rate (eGFR) are important predictors of higher total and cortical volumes. Each increase of eGFR by one unit (i.e., 1 mL/min per 1.73 m2 body surface area) was associated with a 0.98 mL/m2 increase in total kidney volume, and this association was significant. Volumes were lower in persons with eGFR-defined chronic kidney disease.

CONCLUSION

The extraction of image-based biomarkers through CNN-based renal sub-segmentation using data from a population-based study yields reliable results, forming a solid foundation for future investigations.

Sex differences in kidney metabolism may reflect sex-dependent outcomes in human diabetic kidney disease

Diabetic kidney disease (DKD) is the main cause of chronic kidney disease (CKD) and progresses faster in males than in females. We identify sex-based differences in kidney metabolism and in the blood metabolome of male and female individuals with diabetes. Primary human proximal tubular epithelial cells (PTECs) from healthy males displayed increased mitochondrial respiration, oxidative stress, apoptosis, and greater injury when exposed to high glucose compared with PTECs from healthy females. Male human PTECs showed increased glucose and glutamine fluxes to the TCA cycle, whereas female human PTECs showed increased pyruvate content. The male human PTEC phenotype was enhanced by dihydrotestosterone and mediated by the transcription factor HNF4A and histone demethylase KDM6A. In mice where sex chromosomes either matched or did not match gonadal sex, male gonadal sex contributed to the kidney metabolism differences between males and females. A blood metabolomics analysis in a cohort of adolescents with or without diabetes showed increased TCA cycle metabolites in males. In a second cohort of adults with diabetes, females without DKD had higher serum pyruvate concentrations than did males with or without DKD. Serum pyruvate concentrations positively correlated with the estimated glomerular filtration rate, a measure of kidney function, and negatively correlated with all-cause mortality in this cohort. In a third cohort of adults with CKD, male sex and diabetes were associated with increased plasma TCA cycle metabolites, which correlated with all-cause mortality. These findings suggest that differences in male and female kidney metabolism may contribute to sex-dependent outcomes in DKD.

Meta-GWAS on PCSK9 concentrations reveals associations of novel loci outside the PCSK9 locus in White populations

BACKGROUND AND AIMS

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of lipid homeostasis. A few earlier genome-wide association studies (GWAS) investigated genetic variants associated with circulating PCSK9 concentrations. However, uncertainty remains about some of the genetic loci discovered beyond the PCSK9 locus. By conducting the largest PCSK9 meta-analysis of GWAS (meta-GWAS) so far, we aimed to identify novel loci and validate the previously reported loci that regulate PCSK9 concentrations.

METHODS

We performed GWAS for PCSK9 concentrations in two large cohorts (GCKD (n = 4,963) and KORA F3 (n = 2,895)). These were meta-analyzed with previously published data encompassing together 20,579 individuals. We further conducted a second meta-analysis in statin-naïve individuals (n = 15,390). A genetic risk score (GRS) was constructed on PCSK9-increasing SNPs and assessed its impact on the risk for coronary artery disease (CAD) in 394,943 statin-naïve participants (17,077 with events) of the UK Biobank by performing CAD-free survival analysis.

RESULTS

Nine loci were genome-wide significantly associated with PCSK9 concentrations. These included the previously described PCSK9, APOB, KCNA1/KCNA5, and TM6SF2/SUGP1 loci. All imputed SNPs in the PCSK9 locus account for ∼15% of variance of PCSK9 concentrations. We further identified FADS2 as a novel locus that was also found in statin-naïve participants. All imputed SNPs within the FADS2 locus explain ∼1.2% of variance of PCSK9 concentrations. Additionally, four further loci (a region on chromosome 5, SDK1, SPATA16 and HPR) were genome-wide significant in either the main model or the statin-naïve subset. The linear increase in a PCSK9 genetic risk score was associated with 1.41-fold (95%CI 1.16-1.72, p < 0.001) higher risk for incident CAD.

CONCLUSIONS

We identified five novel loci (FADS2, SPATA16, SDK1, HPR and a region on chromosome 5) for PCSK9 concentrations that would require further research. Additionally, we confirm the genome-wide significant loci that were previously detected.

Genetic studies of paired metabolomes reveal enzymatic and transport processes at the interface of plasma and urine

The kidneys operate at the interface of plasma and urine by clearing molecular waste products while retaining valuable solutes. Genetic studies of paired plasma and urine metabolomes may identify underlying processes. We conducted genome-wide studies of 1,916 plasma and urine metabolites and detected 1,299 significant associations. Associations with 40% of implicated metabolites would have been missed by studying plasma alone. We detected urine-specific findings that provide information about metabolite reabsorption in the kidney, such as aquaporin (AQP)-7-mediated glycerol transport, and different metabolomic footprints of kidney-expressed proteins in plasma and urine that are consistent with their localization and function, including the transporters NaDC3 (SLC13A3) and ASBT (SLC10A2). Shared genetic determinants of 7,073 metabolite-disease combinations represent a resource to better understand metabolic diseases and revealed connections of dipeptidase 1 with circulating digestive enzymes and with hypertension. Extending genetic studies of the metabolome beyond plasma yields unique insights into processes at the interface of body compartments.

Uromodulin and its association with urinary metabolites: the German Chronic Kidney Disease Study

BACKGROUND

The progression of chronic kidney disease (CKD), a global public health burden, is accompanied by a declining number of functional nephrons. Estimation of remaining nephron mass may improve assessment of CKD progression. Uromodulin has been suggested as a marker of tubular mass. We aimed to identify metabolites associated with uromodulin concentrations in urine and serum to characterize pathophysiologic alterations of metabolic pathways to generate new hypotheses regarding CKD pathophysiology.

METHODS

We measured urinary and serum uromodulin levels (uUMOD, sUMOD) and 607 urinary metabolites and performed cross-sectional analyses within the German Chronic Kidney Disease study (N = 4628), a prospective observational study. Urinary metabolites significantly associated with uUMOD and sUMOD were used to build weighted metabolite scores for urine (uMS) and serum uromodulin (sMS) and evaluated for time to adverse kidney events over 6.5 years.

RESULTS

Metabolites cross-sectionally associated with uromodulin included amino acids of the tryptophan metabolism, lipids and nucleotides. Higher levels of the sMS [hazard ratio (HR) = 0.73 (95% confidence interval 0.64; 0.82), P = 7.45e-07] and sUMOD [HR = 0.74 (95% confidence interval 0.63; 0.87), P = 2.32e-04] were associated with a lower risk of adverse kidney events over time, whereas uUMOD and uMS showed the same direction of association but were not significant.

CONCLUSIONS

We identified urinary metabolites associated with urinary and serum uromodulin. The sUMOD and the sMS were associated with lower risk of adverse kidney events among CKD patients. Higher levels of sUMOD and sMS may reflect a higher number of functional nephrons and therefore a reduced risk of adverse kidney outcomes.

Genome-wide studies reveal factors associated with circulating uromodulin and its relationships to complex diseases

Uromodulin (UMOD) is a major risk gene for monogenic and complex forms of kidney disease. The encoded kidney-specific protein uromodulin is highly abundant in urine and related to chronic kidney disease, hypertension, and pathogen defense. To gain insights into potential systemic roles, we performed genome-wide screens of circulating uromodulin using complementary antibody-based and aptamer-based assays. We detected 3 and 10 distinct significant loci, respectively. Integration of antibody-based results at the UMOD locus with functional genomics data (RNA-Seq, ATAC-Seq, Hi-C) of primary human kidney tissue highlighted an upstream variant with differential accessibility and transcription in uromodulin-synthesizing kidney cells as underlying the observed cis effect. Shared association patterns with complex traits, including chronic kidney disease and blood pressure, placed the PRKAG2 locus in the same pathway as UMOD. Experimental validation of the third antibody-based locus, B4GALNT2, showed that the p.Cys466Arg variant of the encoded N-acetylgalactosaminyltransferase had a loss-of-function effect leading to higher serum uromodulin levels. Aptamer-based results pointed to enzymes writing glycan marks present on uromodulin and to their receptors in the circulation, suggesting that this assay permits investigating uromodulin's complex glycosylation rather than its quantitative levels. Overall, our study provides insights into circulating uromodulin and its emerging functions.

Association of osteopontin with kidney function and kidney failure in chronic kidney disease patients: the GCKD study

BACKGROUND

Osteopontin (OPN), synthesized in the thick ascending limb of Henle's loop and in the distal tubule, is involved in the pathogenesis of kidney fibrosis, a hallmark of kidney failure (KF). In a cohort of chronic kidney disease (CKD) patients, we evaluated OPN's association with kidney markers and KF.

METHODS

OPN was measured from baseline serum samples of German Chronic Kidney Disease study participants. Cross-sectional regression models for estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (UACR) as well as Cox regression models for all-cause mortality and KF were evaluated to estimate the OPN effect. Additionally, predictive ability, of OPN and time-dependent population-attributable fraction were evaluated.

RESULTS

Over a median follow-up of 6.5 years, 471 KF events and 629 deaths occurred among 4,950 CKD patients. One-unit higher log(OPN) was associated with 5.5 mL/min/1.73m2 lower eGFR (95%CI: [-6.4,-4.6]) and 1% change in OPN with 0.7% higher UACR (estimated effect 0.7, 95%CI: [0.6,0.8]). Moreover, higher OPN levels were associated with a higher risk of KF (hazard ratio [HR] 1.4, 95%CI: [1.2,1.7]) and all-cause mortality (HR 1.5, 95%CI: [1.3,1.8]). After 6 years, 31% of the KF events could be attributed to higher OPN levels (95%CI: [3%,56%]).

CONCLUSIONS

In this study, higher OPN levels were associated with kidney function markers worsening, and a higher risk for adverse outcomes. A larger proportion of KF could be attributed to higher OPN levels warranting further research on OPN with regards to its role in CKD progression and possible treatment options.

MO061: Mri-Based Segmentation of Kidneys in Participants of the German National Cohort (NAKO/GNC) Study

BACKGROUND AND AIMS

Chronic kidney disease (CKD) affects around 10% of adults worldwide and an estimated 13–17% in Germany1. Imaging is a novel, promising approach to identify additional markers of kidney function and CKD2. Within a large, population-based cohort study, the German National Cohort study (NAKO/GNC), 30 000 participants underwent a whole-body MRI protocol3. The goal of our project was to develop an automated kidney segmentation workflow and to examine distributions of the segmented kidneys and kidney sub-compartments.

METHOD

Data from the first 11 207 participants were used to develop a robust image processing pipeline for kidney segmentation and apply it to participants’ abdominal MRI images. After importing 3D gradient echo and 2D haste images into the imaging platform NORA (www.nora-imaging.org), an in-house ‘patchwork’-framework (https://bitbucket.org/reisert/patchwork) based on deep-learning convolutional neural networks was trained on data from 300 persons to automatically segment different kidney compartments (cortex, hilus, medulla and cysts). After an initial training round, the model was improved over four iterations by a loop of prediction, manual correction and retraining. The final model was then applied to the full dataset of 11 207 abdominal MR images, followed by manual quality control prior to statistical analysis. Volumetric parameters for total kidney volume [TKV, defined as cortex + medulla] and compartments were calculated from the segmentations. Values were calculated in absolute units of mL and normalized to body-surface-area (BSA) defined as sqrt(weight in kg*height in cm)/3600.

RESULTS

TKV and the kidney compartments cortex, medulla and hilus could be segmented robustly with the trained network (Fig. 1A). After exclusion of approximately 10% of images because of insufficient segmentation quality due to initial imaging artifacts or poor image quality, the mean (SD) TKV was 364 (±60) mL for men and 290 (±51) mL for women. This difference was markedly attenuated after normalisation to BSA (Fig. 1B). The right kidney was systematically smaller than the left kidney by approximately 5% (Fig. 1C). There was a strong association between participants’ BSA with TKV (Fig. 1D). The normalized kidney sub-compartment volumes showed different patterns across age, with medullary volume decreasing and hilus increasing (Fig. 2).

CONCLUSION

The developed framework enables robust segmentation of kidneys in abdominal MRI data from a nonspecific clinical routine protocol of a large cohort study. Basic parameters such as TKV and sub-compartment volumes of the kidney show correlations with participants’ height, weight, sex and age that are consistent with prior knowledge and may enable an estimation of ‘kidney age’. This is an optimal starting point to identify more advanced imaging biomarkers of kidney function and CKD.

MO517: A Polygenic Risk Score for Reduced EGFR is Associated With Adverse Events in a Chronic Kidney Disease Cohort —the German Chronic Kidney Disease Study

BACKGROUND AND AIMS

Over 10% of the adult population worldwide is affected by chronic kidney disease (CKD). CKD is associated with an increased risk of kidney failure (KF), cardiovascular events and mortality. CKD is defined and staged by estimated glomerular filtration rate (eGFR), the most common measure of kidney function. Genome-wide association studies enable the calculation of polygenic risk scores (PRSs), e.g. for eGFR. The aim of this study was to investigate if a polygenic predisposition to lower eGFR is associated with KF, cardiovascular events and mortality in people with CKD, and if the eGFR PRS carries predictive ability.

METHOD

A PRS for log(eGFR) was developed and tuned in independent, general population-based study samples consisting of European ancestry participants of the UK Biobank and the CKDGen Consortium via the LDpred algorithm [1]. Using genetic information and follow-up data of 4873 participants with moderate CKD enrolled in the German Chronic Kidney Disease study, we calculated, standardized and evaluated the association of the PRS with adverse endpoints. Main endpoints included KF, a composite endpoint of myocardial infarction, cerebral haemorrhage and stroke (3P-MACE), and overall mortality. Cox proportional hazard regression was conducted to estimate (cause-specific) hazard ratios (HRs). Predictive performance of the PRS for KF and 3P-MACE was assessed using prediction error curves and time-dependent c-index. The statistical significance level was Bonferroni-corrected for three main endpoints (P &lt; .05/3).

RESULTS

After a median follow-up time of 6.5 years, 619 patients died, 466 experienced KF, and 545 3P-MACE. Higher levels of the PRS, corresponding to a genetic predisposition to lower eGFR, were associated with higher risk for all three endpoints {KF: HR 1.23, [95% confidence interval (95% CI) 1.12–1.35], 3MACE: 1.15 (1.06–1.25), mortality: 1.12 (1.04;1.22)} after adjusting for baseline age, sex and two principal components. Across deciles of the eGFR PRS, participants in the highest decile, corresponding to the genetically lowest eGFR, had a &gt;2-fold increased risk of KF compared with those in the lowest decile [HR = 2.13 (1.39–3.27), Fig. 1]. No distinct improvement in the prediction performance for KF was observed when adding the PRS to the well-established KF risk equation by Tangri et al. [2]. This also held true for the added predictive ability of the PRS for 3P-MACE when compared with a model with established cardiovascular risk factors.

CONCLUSION

Our study revealed a significant association between a polygenic predisposition to lower eGFR and KF, cardiovascular events, and mortality among people with moderate CKD, emphasizing the importance of genetic background even after disease onset. The eGFR PRS carried no added predictive ability with regard to KF and 3P-MACE beyond established risk factors.

MO513: Implications of Using Various Equations to Estimate Glomerular Filtration Rate in the GNC (NAKO) Study

BACKGROUND AND AIMS

Glomerular filtration rate (GFR) is the most common measure of kidney function. Measuring GFR is often infeasible in routine clinical practice and population studies, where it is estimated instead from blood biomarkers. Three currently recommended equations, eGFR(crea), eGFR(cystC) and eGFR(cr + cy), use either creatinine, cystatin C or both, respectively, to calculate eGFR [1]. In addition, three alternative equations were introduced recently: two of them update eGFR(crea) and eGFR(cr + cy) by excluding the race term used in them [2], and the full age spectrum (FAS) equation (creatinine-based), which was specifically developed to estimate GFR across the full age range [3]. We aimed to assess the impact of these six equations on GFR estimates and the proportion of participants with chronic kidney disease (CKD) in the German National Cohort (GNC, NAKO) Study.

METHOD

The NAKO study is a prospective cohort study in Germany. Data to estimate GFR (eGFR) using the six equations was available for 112 843 participants aged 19–75 years, mostly of European ancestry. Pairwise Spearman correlation coefficients between GFR estimates were calculated. CKD was defined as an eGFR &lt;60 mL/min/1.73 m² for each calculation. Agreement between CKD status derived from the different GFR equations was assessed using Cohen's κ. Measured GFR was not available.

RESULTS

Median eGFR/equation ranged from 92.2 mL/min/1.73 m² using the new FAS-equation [3] to 105.7 mL/min/1.73 m² using the updated race-free eGFR(cr + cy)2 (Fig. 1). eGFR values of the three equations using creatinine only, as well as eGFR values from the two equations using both creatinine and cystatin C, correlated well (r &gt; 0.95), while the correlation of GFR estimates based on equations either using creatinine or cystatin C was only moderate (r = 0.6, Fig. 1).

The frequency of CKD ranged from 1.0% to 2.3%, a &gt;2-fold difference. The agreement assessed as Cohen's κ was the smallest when comparing the CKD status based on eGFR(cy) [1] with the CKD status based on the updated race-free eGFR (crea) [2] (Cohen's κ = 0.38). While both equations led to a mutual CKD classification in 707 participants (0.6%), 613 (0.5%) were only classified as having CKD when the updated race-free eGFR (crea) [2] was used, and 1580 (1.4%) were only classified as having CKD using eGFR (cy) [1]. Interestingly, the respective serum biomarker that led to the discordant classification of CKD was abnormally high, while the other biomarker was mainly in the normal range, highlighting the potential influence of non-kidney related factors on biomarker levels that influence estimates of CKD prevalence.

CONCLUSION

The use of different GFR equations leads to variable estimates, affecting the proportion classified as having CKD. Non-GFR determinants with an impact on the levels of either creatinine or cystatin C may lead to incorrect estimates of GFR and affect CKD prevalence estimates, which underscores the utility of a joint view using various equations.

MO048: Genome-wide studies reveal factors associated with circulating uromodulin and its relations with complex diseases

BACKGROUND AND AIMS

UMOD is a major risk gene for monogenic and complex forms of kidney disease. The encoded kidney-specific protein uromodulin is the most abundant protein in urine and related to chronic kidney disease, hypertension and pathogen defense. Through basolateral release from kidney epithelial cells, uromodulin also reaches the blood, where its function is largely unknown. To gain insights into potential systemic roles, we performed genome-wide screens of circulating uromodulin in seven cohorts using two complementary assays.

METHOD

Separate genome-wide association study meta-analyses for circulating uromodulin were conducted for the antibody-based assay (five cohorts, N = 13 985) and the aptamer-based SOMAscan assay (two cohorts, N = 18 070). Genome-wide significant loci were placed into their functional genomic context using RNA-seq, ATAC-seq and Hi-C data generated from primary human kidney tissue. An array of downstream genetic analyses was then performed for significant loci, including fine-mapping, colocalization analyses and gene-by-gene interaction analyses. The B4GALNT2 p.Cys466Arg allele was expressed in MDCK cells and studied by immunofluorescence and Western blotting analyses.

RESULTS

We detected and replicated 13 genome-wide significant loci (P &lt;5e−8; 12 novel). At the UMOD locus, functional genomics data of primary human kidney tissue highlighted an upstream regulatory variant with differential accessibility and UMOD transcription in uromodulin-synthesizing kidney cells. Shared association patterns with complex traits, including chronic kidney disease and blood pressure, placed the PRKAG2 locus in the same context as UMOD. Experimental validation of another locus, B4GALNT2, showed that the detected p.Cys466Arg variant of the encoded N-acetylgalactosaminyltransferase has a loss-of-function effect leading to higher serum uromodulin levels. Lastly, our results point to enzymes writing glycan marks present on uromodulin and to their receptors in the circulation.

CONCLUSION

This study provides human genetic evidence of new pathway members of uromodulin and delivers novel insights into its determinants and systemic role in the circulation.

Genetics of osteopontin in patients with chronic kidney disease: The German Chronic Kidney Disease study

Osteopontin (OPN), encoded by SPP1, is a phosphorylated glycoprotein predominantly synthesized in kidney tissue. Increased OPN mRNA and protein expression correlates with proteinuria, reduced creatinine clearance, and kidney fibrosis in animal models of kidney disease. But its genetic underpinnings are incompletely understood. We therefore conducted a genome-wide association study (GWAS) of OPN in a European chronic kidney disease (CKD) population. Using data from participants of the German Chronic Kidney Disease (GCKD) study (N = 4,897), a GWAS (minor allele frequency [MAF]≥1%) and aggregated variant testing (AVT, MAF<1%) of ELISA-quantified serum OPN, adjusted for age, sex, estimated glomerular filtration rate (eGFR), and urinary albumin-to-creatinine ratio (UACR) was conducted. In the project, GCKD participants had a mean age of 60 years (SD 12), median eGFR of 46 mL/min/1.73m2 (p25: 37, p75: 57) and median UACR of 50 mg/g (p25: 9, p75: 383). GWAS revealed 3 loci (p<5.0E-08), two of which replicated in the population-based Young Finns Study (YFS) cohort (p<1.67E-03): rs10011284, upstream of SPP1 encoding the OPN protein and related to OPN production, and rs4253311, mapping into KLKB1 encoding prekallikrein (PK), which is processed to kallikrein (KAL) implicated through the kinin-kallikrein system (KKS) in blood pressure control, inflammation, blood coagulation, cancer, and cardiovascular disease. The SPP1 gene was also identified by AVT (p = 2.5E-8), comprising 7 splice-site and missense variants. Among others, downstream analyses revealed colocalization of the OPN association signal at SPP1 with expression in pancreas tissue, and at KLKB1 with various plasma proteins in trans, and with phenotypes (bone disorder, deep venous thrombosis) in human tissue. In summary, this GWAS of OPN levels revealed two replicated associations. The KLKB1 locus connects the function of OPN with PK, suggestive of possible further post-translation processing of OPN. Further studies are needed to elucidate the complex role of OPN within human (patho)physiology.

PCSK9 and Cardiovascular Disease in Individuals with Moderately Decreased Kidney Function

Background and objectives: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of lipid homeostasis. Studies investigating the association between PCSK9 and cardiovascular disease in large cohorts of CKD patients are limited. Design, setting, participants, and measurements: The association of PCSK9 concentrations with prevalent and incident cardiovascular disease was investigated in 5,138 Caucasians of the German Chronic Kidney Disease study with a median follow-up of 6.5 years. Inclusion criteria were eGFR of 30-60 mL/min/1.73 m² or an eGFR>60 mL/min/1.73m² in the presence of overt proteinuria (urine albumin-creatinine ratio >300mg/g or equivalent). Prevalent cardiovascular disease was defined as history of non-fatal myocardial infarction, coronary artery bypass grafting, percutaneous transluminal coronary angioplasty, carotid arteries interventions and stroke. Incident major adverse cardiovascular disease events included death from cardiovascular causes, acute non-fatal myocardial infarction and non-fatal stroke. Results: Median PCSK9 concentration in the cohort was 285 ng/mL (interquartile range 231-346 ng/mL). There was no association between PCSK9 concentrations and baseline eGFR and albuminuria. With each 100 ng/ml increment of PCSK9, the odds for prevalent cardiovascular disease (n=1,284) was 1.22-fold (95%CI 1.12-1.34, p<0.001) higher in a model with extended adjustment for major confounders. This association was stronger in non-statin than statin-users (p-value for interaction=0.009). During follow-up 474 individuals experienced a major adverse cardiovascular disease event and participants in PCSK9 quartiles 2 to 4 had a 32%-47% higher risk compared to quartile 1 (p<0.05). Subgroup analysis revealed this association was restricted to those participants who already had cardiovascular disease at baseline (all HR>1.75, p<0.05). In addition, PCSK9 showed a valuable gain in classification accuracy both for prevalent cardiovascular disease (NRI=0.27, 95%CI:0.20-0.33) and incident major adverse cardiovascular disease events during follow-up (NRI=0.10, 95%CI:0.008-0.21) when added to an extended adjustment model. Conclusions: Our findings reveal no relation of PCSK9 with baseline eGFR and albuminuria, but a significant association between higher PCSK9 concentrations and risk of cardiovascular disease independent of traditional risk factors including LDL-cholesterol levels.

Self-Reported Medication Use and Urinary Drug Metabolites in the German Chronic Kidney Disease (GCKD) Study

BACKGROUND

Polypharmacy is common among patients with CKD, but little is known about the urinary excretion of many drugs and their metabolites among patients with CKD.

METHODS

To evaluate self-reported medication use in relation to urine drug metabolite levels in a large cohort of patients with CKD, the German Chronic Kidney Disease study, we ascertained self-reported use of 158 substances and 41 medication groups, and coded active ingredients according to the Anatomical Therapeutic Chemical Classification System. We used a nontargeted mass spectrometry-based approach to quantify metabolites in urine; calculated specificity, sensitivity, and accuracy of medication use and corresponding metabolite measurements; and used multivariable regression models to evaluate associations and prescription patterns.

RESULTS

Among 4885 participants, there were 108 medication-drug metabolite pairs on the basis of reported medication use and 78 drug metabolites. Accuracy was excellent for measurements of 36 individual substances in which the unchanged drug was measured in urine (median, 98.5%; range, 61.1%-100%). For 66 pairs of substances and their related drug metabolites, median measurement-based specificity and sensitivity were 99.2% (range, 84.0%-100%) and 71.7% (range, 1.2%-100%), respectively. Commonly prescribed medications for hypertension and cardiovascular risk reduction-including angiotensin II receptor blockers, calcium channel blockers, and metoprolol-showed high sensitivity and specificity. Although self-reported use of prescribed analgesics (acetaminophen, ibuprofen) was <3% each, drug metabolite levels indicated higher usage (acetaminophen, 10%-26%; ibuprofen, 10%-18%).

CONCLUSIONS

This comprehensive screen of associations between urine drug metabolite levels and self-reported medication use supports the use of pharmacometabolomics to assess medication adherence and prescription patterns in persons with CKD, and indicates under-reported use of medications available over the counter, such as analgesics.

A Predictive Model for Progression of CKD to Kidney Failure Based on Routine Laboratory Tests

RATIONALE & OBJECTIVE

Stratification of chronic kidney disease (CKD) patients at risk for progressing to end-stage kidney disease (ESKD) requiring kidney replacement therapy (KRT) is important for clinical decision-making and trial enrollment.

STUDY DESIGN

Four independent prospective observational cohort studies.

SETTING & PARTICIPANTS

The development cohort was comprised of 4,915 CKD patients and three independent validation cohorts were comprised of a total of 3,063. Patients were followed-up for approximately five years.

NEW PREDICTORS & ESTABLISHED PREDICTORS

22 demographic, anthropometric and laboratory variables commonly assessed in CKD patients.

OUTCOMES

Progression to ESKD requiring KRT.

ANALYTICAL APPROACH

A Least Absolute Shrinkage and Selection Operator (LASSO) Cox proportional hazards model was fit to select laboratory variables that best identified patients at high risk for ESKD. Model discrimination and calibration were assessed and compared against the 4-variable Tangri (T4) risk equation. Both used a resampling approach within the development cohort and in the validation cohorts using cause-specific concordance (C) statistics, net reclassification improvement, and calibration graphs.

RESULTS

The newly derived 6-variable (Z6) risk score included serum creatinine, albumin, cystatin C and urea, as well as hemoglobin and the urine albumin-to-creatinine ratio. Based on the resampling approach, Z6 achieved a median C value of 0.909 (95% CI, 0.868-0.937) at two years after the baseline visit, whereas the T4 achieved a median C value of 0.855 (95% CI, 0.799-0.915). In the three independent validation cohorts, Z6 C values were 0.894, 0.921, and 0.891, whereas the T4 C values were 0.882, 0.913, and 0.862.

LIMITATIONS

The Z6 was both derived and tested only in White European cohorts.

CONCLUSIONS

A new risk equation, based on six routinely available laboratory tests facilitates identification of patients with CKD who are at high risk of progressing to ESKD.

MO492SELF-REPORTED MEDICATION USE AND URINARY DRUG METABOLITES IN THE GERMAN CHRONIC KIDNEY DISEASE (GCKD) STUDY: A PHARMACOMETABOLOMIC APPROACH

Background and Aims

Chronic kidney disease (CKD) patients are prone to prescription of multiple medications. Medication adherence is a well-recognized problem in the management of patients with chronic diseases requiring polypharmacy. This study aimed to evaluate the connection between self-reported medication use and urine drug metabolite levels in a large cohort of CKD patients, the GCKD study, as a basis for future pharmacometabolomics studies.

Method

Self-reported medication use of 160 substances and 41 medication groups was ascertained at study baseline and coded according to the Anatomical Therapeutic Chemical classification system. A non-targeted mass spectrometry-based approach (Metabolon HD4™) was used for concomitant metabolite quantification in urine. Specificity, sensitivity and accuracy of medication use and the corresponding urine metabolite measurements were calculated. Multivariable regression models (adjusted to age, sex, eGFR, log(UACR), systolic blood pressure, LDL, log(triglycerides), log(HBA1c) were used to establish associations in prescription patterns.

Results

Among 4,885 participants, 78 drug metabolites were detected in urine (frequency range: 0.4-58%) and assigned into 110 medication – drug metabolite pairs (MMPs) based on reported individual substances and medication groups. For all 68 MMPs of individual substances, accuracy of medication use and the corresponding drug metabolite measurement was excellent (median 97.0%, range 43%-100%), as was measurement-based specificity (median 99.3%, range 73.3%-100%; Fig. 1). Median measurement-based sensitivity was 72.1% (range 1.1%-100%, Fig. 1). Sensitivity and specificity were especially high for angiotensin-II receptor blockers (92%-96%; 99-100%), calcium channel blockers (85-100%; 91-100%), and metoprolol (90%; 98% respectively) commonly prescribed and important medications for blood pressure control and cardiovascular risk reduction in CKD patients. MMPs showing sensitivity &lt;80% included several substances found in over-the-counter (OTC) analgesic medications, suggesting that their use is not always reported. While self-reported use of the OTC analgesics acetaminophen and ibuprofen was &lt;3% each, their corresponding drug metabolites indicated higher usage (acetaminophen: 10-26%; ibuprofen: 10-18%, depending on the number of evaluated drug metabolites). Typical examples of medication co-prescriptions (e.g., trimethoprim and sulfamethoxazole) were detected as the combined presence of their drug metabolites in urine. This result validates the abstraction of single substances from combination medications and this urine-based metabolomic approach.

Conclusion

This study provides a comprehensive screen of the associations between urine drug metabolite levels and self-reported medication use. It supports the usefulness of pharmacometabolomics to assess medication use, frequency of OTC analgesics use, and prescription patterns in persons with CKD.

FC 061OSTEOPONTIN AND ITS ASSOCIATION WITH ADVERSE EVENTS IN THE GERMAN CHRONIC KIDNEY DISEASE STUDY

Background and Aims

Osteopontin (OPN) is synthesized in the thick ascending limb of Henle’s loop and in the distal tubule. Numerous studies have shown that OPN mRNA and protein expression is increased in animal models of many different renal diseases, especially glomerular diseases as well as diabetic nephropathy. Here, high OPN expression correlated with proteinuria, reduction of creatinine clearance, fibrosis as well as macrophage and T-cell infiltration. OPN has therefore been suggested to be a promising biomarker for various kidney diseases. Further studies are needed to fully understand its role in kidney (patho-)physiology and its potential as a marker of kidney disease progression and adverse renal events. We therefore evaluated the association of OPN with kidney events and all-cause mortality in a cohort of CKD patients, the German Chronic Kidney Disease (GCKD) study.

Method

OPN was measured from baseline serum samples using the Quantikine Human OPN Immunoassay. Coefficients of variation were &lt;7%. Kidney events included kidney failure treated with kidney replacement therapy (dialysis, transplantation), and death due to discontinuation of dialysis treatment. Another event of interest was all-cause mortality. All events were abstracted from hospital discharge letters and death certificates by trained physicians based on a standardized endpoint catalogue. Cross-sectional regression models (dependent variables: eGFR, logUACR) adjusted for confounding variables (Table 1 legend) were fitted. Multi-variable adjusted Cox proportional hazard regression analyses were conducted. Estimated risks are expressed as cause-specific hazard ratios (HR) for all-cause mortality and kidney events, with death of other causes as the competing event. Sensitivity analyses included evaluation of all models stratified by the three most common causes of kidney disease in GCKD: hypertensive nephropathy, primary glomerular disease, and diabetic nephropathy.

Results

Over 6.5 years of follow-up, 473 kidney events and 582 deaths occurred among 4,950 GCKD patients. Hundred-and-forty-eight deaths and 62 kidney events occurred in 1,143 hypertensive nephropathy patients, 49 deaths and 118 kidney events occurred in 935 primary glomerular nephropathy patients, and 170 deaths and 99 kidney events in diabetic nephropathy patients (Table 1). Overall mean age was 60.1 years (±12.0), with 60.3% men. Median OPN levels were 29.2 ng/mL (IQR 21.2). Cross-sectionally a 10% change in OPN was associated with 0.5% lower eGFR on average (p&lt;0.0001, 95% CI: -6.4 to -4.6) and a 7% change in UACR (p&lt;0.0001, 95% CI: 0.6 to 0.8) overall. Stratified by leading cause of kidney disease, results for eGFR and UACR were of similar direction for all groups (Table 1 A). After adjusting for baseline eGFR and UACR (Table 1 B), higher OPN levels were associated with a higher risk of kidney events overall (HR 1.4, p&lt;0.001, 95% CI 1.1-1.7). For patients with diabetic nephropathy this risk was even higher (HR 2.2, p&lt;0.01, 95% CI 1.4-3.6). Higher OPN levels were also associated with higher risk of all-cause mortality overall (HR 1.5, p&lt;0.0001, 95% CI 1.3-1.8) as well as for diabetic nephropathy patients (HR 1.7, p&lt;0.01, 95% CI 1.2-2.4). HRs for the hypertensive nephropathy and primary glomerular nephropathy groups showed mostly the same effect directions, but did not reach significance after adjustment.

Conclusion

Higher OPN levels were associated with lower eGFR and higher UACR cross-sectionally and significantly associated with a higher risk of renal events and all-cause mortality especially for diabetic nephropathy patients even after adjustment for baseline eGFR, UACR and other confounding factors. These results are supportive of OPN being a potential marker of CKD progression and mortality.

MO482URINE METABOLITE LEVELS OF CKD PATIENTS ARE ASSOCIATED WITH ADVERSE KIDNEY OUTCOMES AND MORTALITY*

Background and Aims

Chronic kidney disease (CKD) affects &gt;10% of the adult population worldwide and is associated with increased risk of kidney failure (KF) and mortality. Mechanisms underlying the variable course of disease progression are incompletely understood. This study aimed at identifying novel metabolite biomarkers of adverse kidney outcomes and overall mortality, which may offer insights into pathophysiological mechanisms.

Method

Using measurements of 1,487 metabolites in urine of 5,087 CKD patients enrolled in the German Chronic Kidney Disease study, we evaluated the association of urine metabolite levels with adverse events. Main endpoints include KF, a combined endpoint of KF and acute kidney injury (KF+AKI), and overall mortality. Statistical analysis was based on a discovery-replication design (ratio 2:1) and multivariable adjusted Cox regression models. We performed cause-specific hazard regression as well as subdistribution hazard analyses with death of other causes as a competing event for the endpoints KF and KF+AKI. Statistical significance was defined using a Bonferroni correction for the number of tested metabolites per stage. An association was considered replicated if effect estimates from both stages were significant and direction-consistent.

Results

Median follow-up time was 4 years. At time of analysis, 362 patients died, 241 experienced KF, and 382 KF+AKI. Overall, we identified 55 urine metabolites whose levels were significantly and reproducibly associated with adverse kidney outcomes and/or mortality. Cause-specific and subdistribution hazard analyses showed almost identical results. Higher levels of the amino acid C-glycosyltryptophan in urine were associated with higher risk for all three endpoints (KF: hazard ratio 1.43, 95% confidence interval [1.27;1.61], KF+AKI: 1.40 [1.27;1.55], mortality: 1.47 [1.33;1.63]). The cumulative incidence function of KF was higher for each quartile of urine C-glycosyltryptophan levels and the effect were most pronounced in the highest quartile (see Figure). The replicated metabolites belong to different biochemical classes, and those belonging to the phosphatidylcholines pathway showed enrichment. Members of this pathway contributed to the improvement of the prediction performance for KF observed when multiple metabolites were added to the well-established kidney failure risk equation by Tangri.

Conclusion

This comprehensive screen of the association between urine metabolite levels and adverse kidney outcomes and mortality identified and replicated 55 urine metabolites associated with adverse kidney events, potentially providing new insights into the mechanisms of kidney disease progression. The study represents a valuable resource for future experimental studies of biomarkers of CKD progression.

Urine Metabolite Levels, Adverse Kidney Outcomes, and Mortality in CKD Patients: A Metabolome-wide Association Study

RATIONALE & OBJECTIVE

Mechanisms underlying the variable course of disease progression in patients with chronic kidney disease (CKD) are incompletely understood. The aim of this study was to identify novel biomarkers of adverse kidney outcomes and overall mortality, which may offer insights into pathophysiologic mechanisms.

STUDY DESIGN

Metabolome-wide association study.

SETTING & PARTICIPANTS

5,087 patients with CKD enrolled in the observational German Chronic Kidney Disease Study.

EXPOSURES

Measurements of 1,487 metabolites in urine.

OUTCOMES

End points of interest were time to kidney failure (KF), a combined end point of KF and acute kidney injury (KF+AKI), and overall mortality.

ANALYTICAL APPROACH

Statistical analysis was based on a discovery-replication design (ratio 2:1) and multivariable-adjusted Cox regression models.

RESULTS

After a median follow-up of 4 years, 362 patients died, 241 experienced KF, and 382 experienced KF+AKI. Overall, we identified 55 urine metabolites whose levels were significantly associated with adverse kidney outcomes and/or mortality. Higher levels of C-glycosyltryptophan were consistently associated with all 3 main end points (hazard ratios of 1.43 [95% CI, 1.27-1.61] for KF, 1.40 [95% CI, 1.27-1.55] for KF+AKI, and 1.47 [95% CI, 1.33-1.63] for death). Metabolites belonging to the phosphatidylcholine pathway showed significant enrichment. Members of this pathway contributed to the improvement of the prediction performance for KF observed when multiple metabolites were added to the well-established Kidney Failure Risk Equation.

LIMITATIONS

Findings among patients of European ancestry with CKD may not be generalizable to the general population.

CONCLUSIONS

Our comprehensive screen of the association between urine metabolite levels and adverse kidney outcomes and mortality identifies metabolites that predict KF and represents a valuable resource for future studies of biomarkers of CKD progression.

pgainsim: an R-package to assess the mode of inheritance for quantitative trait loci in GWAS

MOTIVATION

When performing genome-wide association studies conventionally the additive genetic model is used to explore whether a single nucleotide polymorphism (SNP) is associated with a quantitative trait. But for variants, which do not follow an intermediate mode of inheritance (MOI), the recessive or the dominant genetic model can have more power to detect associations and furthermore the MOI is important for downstream analyses and clinical interpretation. When multiple MOIs are modelled the question arises, which describes the true underlying MOI best.

RESULTS

We developed an R-package allowing for the first time to determine study specific critical values when one of the three models is more informative than the other ones for a quantitative trait locus. The package allows for user-friendly simulations to determine these critical values with predefined minor allele frequencies and study sizes. For application scenarios with extensive multiple testing we integrated an interpolation functionality to determine critical values already based on a moderate number of random draws.

AVAILABILITY AND IMPLEMENTATION

The R-package pgainsim is freely available for download on Github at https://github.com/genepi-freiburg/pgainsim.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Thyroid function, renal events and mortality in chronic kidney disease patients: the German Chronic Kidney Disease study

BACKGROUND

Hypothyroidism and low free triiodothyronine (FT3) syndrome [low FT3 levels with normal thyroid-stimulating hormone (TSH)] have been associated with reduced kidney function cross-sectionally in chronic kidney disease (CKD) patients with severely reduced estimated glomerular filtration rate (eGFR) or end-stage kidney disease (ESKD). Results on the prospective effects of impaired thyroid function on renal events and mortality for patients with severely reduced eGFR or from population-based cohorts are conflicting. Here we evaluated the association between thyroid and kidney function with eGFR (cross-sectionally) as well as renal events and mortality (prospectively) in a large, prospective cohort of CKD patients with mild to moderately reduced kidney function.

METHODS

Thyroid markers were measured among CKD patients from the German Chronic Kidney Disease study. Incident renal endpoints (combined ESKD, acute kidney injury and renal death) and all-cause mortality were abstracted from hospital records and death certificates. Time to first event analysis of complete data from baseline to the 4-year follow-up (median follow-up time 4.04 years) of 4600 patients was conducted. Multivariable linear regression and Cox proportional hazards models were fitted for single and combined continuous thyroid markers [TSH, free thyroxine (FT4), FT3] and thyroid status.

RESULTS

Cross-sectionally, the presence of low-FT3 syndrome showed a significant inverse association with eGFR and continuous FT3 levels alone showed a significant positive association with eGFR; in combination with FT4 and TSH, FT3 levels also showed a positive association and FT4 levels showed a negative association with eGFR. Prospectively, higher FT4 and lower FT3 levels were significantly associated with a higher risk of all-cause mortality (N events = 297). Per picomole per litre higher FT3 levels the risk of reaching the composite renal endpoint was 0.73-fold lower (95% confidence interval 0.65-0.82; N events = 615). Compared with euthyroid patients, patients with low-FT3 syndrome had a 2.2-fold higher risk and patients with hypothyroidism had a 1.6-fold higher risk of experiencing the composite renal endpoint.

CONCLUSIONS

Patients with mild to moderate CKD suffering from thyroid function abnormalities are at an increased risk of adverse renal events and all-cause mortality over time.

Rare genetic variants affecting urine metabolite levels link population variation to inborn errors of metabolism

Metabolite levels in urine may provide insights into genetic mechanisms shaping their related pathways. We therefore investigate the cumulative contribution of rare, exonic genetic variants on urine levels of 1487 metabolites and 53,714 metabolite ratios among 4864 GCKD study participants. Here we report the detection of 128 significant associations involving 30 unique genes, 16 of which are known to underlie inborn errors of metabolism. The 30 genes are strongly enriched for shared expression in liver and kidney (odds ratio = 65, p-FDR = 3e-7), with hepatocytes and proximal tubule cells as driving cell types. Use of UK Biobank whole-exome sequencing data links genes to diseases connected to the identified metabolites. In silico constraint-based modeling of gene knockouts in a virtual whole-body, organ-resolved metabolic human correctly predicts the observed direction of metabolite changes, highlighting the potential of linking population genetics to modeling. Our study implicates candidate variants and genes for inborn errors of metabolism.

Clinical decision making in small non-functioning VHL-related incidentalomas

The optimal treatment strategy for patients with small non-functioning VHL-related incidentalomas is unclear. We searched the Freiburg VHL registry for patients with radiologic evidence of pheochromocytoma/paraganglioma (PHEO/PGL). In total, 176 patients with single, multiple, and recurrent tumours were identified (1.84 tumours/patient, range 1-8). Mean age at diagnosis was 32 ± 16 years. Seventy-four percent of tumours were localised to the adrenals. Mean tumour diameter was 2.42 ± 2.27 cm, 46% were <1.5 cm. 24% of tumours were biochemically inactive. Inactive tumours were significantly smaller than active PHEO/PGL at diagnosis (4.16 ± 2.80 cm vs 1.43 ± 0.45 cm; P < 0.025) and before surgery (4.89 ± 3.47 cm vs 1.36 ± 0.43 cm; P < 0.02). Disease was stable in 67% of 21 patients with evaluable tumours ≤1.5 cm according to RECIST and progressed in 7. Time till surgery in these patients was 29.5 ± 20.0 months. A total of 155 patients underwent surgery. PHEO/PGL was histologically excluded in 4 and proven in 151. Of these, one had additional metastatic disease, one harboured another tumour of a different type, and in 2 a second surgery for suspected disease recurrence did not confirm PHEO/PGL. Logistic regression analysis revealed 50% probability for a positive/negative biochemical test result at 1.8 cm tumour diameter. Values of a novel symptom score were positively correlated with tumour size (Rs = 0.46, P < 0.0001) and together with a positive biochemistry a linear size predictor (P < 0.01). Results support standardised clinical assessment and measurement of tumour size and metanephrines in VHL patients with non-functioning incidentalomas <1.5 cm at one year following diagnosis and at individualised intervals thereafter depending on evolving growth dynamics, secretory activity and symptomatology.

The relationship between blood metabolites of the tryptophan pathway and kidney function: a bidirectional Mendelian randomization analysis

Blood metabolites of the tryptophan pathway were found to be associated with kidney function and disease in observational studies. In order to evaluate causal relationship and direction, we designed a study using a bidirectional Mendelian randomization approach. The analyses were based on published summary statistics with study sizes ranging from 1,960 to 133,413. After correction for multiple testing, results provided no evidence of an effect of metabolites of the tryptophan pathway on estimated glomerular filtration rate (eGFR). Conversely, lower eGFR was related to higher levels of four metabolites: C-glycosyltryptophan (effect estimate = − 0.16, 95% confidence interval [CI] (− 0.22; − 0.1); p = 9.2e−08), kynurenine (effect estimate = − 0.18, 95% CI (− 0.25; − 0.11); p = 1.1e−06), 3-indoxyl sulfate (effect estimate = − 0.25, 95% CI (− 0.4; − 0.11); p = 6.3e−04) and indole-3-lactate (effect estimate = − 0.26, 95% CI (− 0.38; − 0.13); p = 5.4e−05). Our study supports that lower eGFR causes higher blood metabolite levels of the tryptophan pathway including kynurenine, C-glycosyltryptophan, 3-indoxyl sulfate, and indole-3-lactate. These findings aid the notion that metabolites of the tryptophan pathway are a consequence rather than a cause of reduced eGFR. Further research is needed to specifically examine relationships with respect to chronic kidney disease (CKD) progression among patients with existing CKD.

Urine 6-Bromotryptophan: Associations with Genetic Variants and Incident End-Stage Kidney Disease

Higher serum 6-bromotryptophan has been associated with lower risk of chronic kidney disease (CKD) progression, implicating mechanisms beyond renal clearance. We studied genetic determinants of urine 6-bromotryptophan and its association with CKD risk factors and incident end-stage kidney disease (ESKD) in 4,843 participants of the German Chronic Kidney Disease (GCKD) study. 6-bromotryptophan was measured from urine samples using mass spectrometry. Patients with higher levels of urine 6-bromotryptophan had higher baseline estimated glomerular filtration rate (eGFR, p < 0.001). A genome-wide association study of urine 6-bromotryptophan identified two significant loci possibly related to its tubular reabsorption, SLC6A19, and its production, ERO1A, which was also associated with serum 6-bromotryptophan in an independent study. The association between urine 6-bromotryptophan and time to ESKD was assessed using Cox regression. There were 216 ESKD events after four years of follow-up. Compared with patients with undetectable levels, higher 6-bromotryptophan levels were associated with lower risk of ESKD in models unadjusted and adjusted for ESKD risk factors other than eGFR ( Collapse

Key Words

• prognostic markers
• kidney diseases
• biomarkers
• epidemiology
• genetics research
• outcomes research
• risk factors

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MESH Headings

• Amino Acid Transport Systems, Neutral/genetics
• Female
• Genetic Predisposition to Disease/genetics
• Genetic Variation/genetics
• Glomerular Filtration Rate/genetics
• Humans
• Kidney Failure, Chronic/epidemiology
• Kidney Failure, Chronic/genetics
• Kidney Failure, Chronic/urine
• Male
• Membrane Glycoproteins/genetics
• Middle Aged
• Oxidoreductases/genetics
• Proportional Hazards Models
• Risk Factors
• Tryptophan/analogs & derivatives
• Tryptophan/urine

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Grants

• R21 DK112087 NIDDK NIH HHS
• UL1 RR025005 NCRR NIH HHS
• R01 HL086694 NHLBI NIH HHS
• U01 HG004402 NHGRI NIH HHS
• HHSN268201700002C NHLBI NIH HHS
• HHSN268201700001I NHLBI NIH HHS
• HHSN268201700004I NHLBI NIH HHS
• HHSN268201700004C NHLBI NIH HHS
• R01 HL087641 NHLBI NIH HHS
• HHSN268201700003I NHLBI NIH HHS
• HHSN268201700005C NHLBI NIH HHS
• HHSN268201700001C NHLBI NIH HHS
• HHSN268201700003C NHLBI NIH HHS
• HHSN268201700002I NHLBI NIH HHS
• HHSN268201700005I NHLBI NIH HHS

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Affiliation(s)

Peggy Sekula Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
Adrienne Tin Division of Nephrology, Department of Medicine, University of Mississippi Medical Center, Jackson, MS, USA The Memory Impairment and Neurodegenerative Dementia Center, University of Mississippi Medical Center, Jackson, MS, USA
Ulla T Schultheiss Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany Division of Nephrology, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
Seema Baid-Agrawal Department of Nephrology and Transplant Center, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden
Robert P Mohney Metabolon Inc., Durham, NC, USA
Inga Steinbrenner Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany
Bing Yu School of Public Health, The University of Texas Health Science Center at Houston, Houston, USA
Shengyuan Luo Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, MD, USA
Eric Boerwinkle School of Public Health, The University of Texas Health Science Center at Houston, Houston, USA
Kai-Uwe Eckardt Department of Nephrology and Medical Intensive Care, Charité - Universitätsmedizin Berlin, Berlin, Germany Department of Nephrology and Hypertension, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054, Erlangen, Germany
Josef Coresh Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, MD, USA
Morgan E Grams Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, MD, USA Division of Nephrology, Johns Hopkins School of Medicine, Baltimore, MD, USA
Anna Kӧttgen Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.

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Design choices for observational studies of the effect of exposure on disease incidence

The purpose of this paper is to help readers choose an appropriate observational study design for measuring an association between an exposure and disease incidence. We discuss cohort studies, sub-samples from cohorts (case-cohort and nested case-control designs), and population-based or hospital-based case-control studies. Appropriate study design is the foundation of a scientifically valid observational study. Mistakes in design are often irremediable. Key steps are understanding the scientific aims of the study and what is required to achieve them. Some designs will not yield the information required to realise the aims. The choice of design also depends on the availability of source populations and resources. Choosing an appropriate design requires balancing the pros and cons of various designs in view of study aims and practical constraints. We compare various cohort and case-control designs to estimate the effect of an exposure on disease incidence and mention how certain design features can reduce threats to study validity.

Growth characteristics and therapeutic decision markers in von Hippel-Lindau disease patients with renal cell carcinoma

Background

Von Hippel-Lindau (VHL) disease is a multi-systemic hereditary disease associated with several benign and malignant tumor entities, including clear cell renal cell carcinoma (ccRCC). Since ccRCCs grow slowly, nephron sparing surgery is typically performed at a tumor diameter of 3–4 cm before the tumor metastasizes. However, in the case of recurrent disease, repeated surgical intervention can impair renal function. Therefore, it is crucial to optimize the timing for surgical interventions through a better understanding of the growth kinetics of ccRCCs in VHL. We investigated tumor growth kinetics and modern volumetric assessment to guide future therapeutic decisions.

Results

The prevalence of ccRCC was 28% in a cohort of 510 VHL patients. Of 144 patients with ccRCC, 41 were followed with serial imaging which identified 102 renal tumors, which exhibited heterogeneous growth kinetics. ccRCCs grew at an average absolute growth rate of 0.287 cm/year, an average relative growth rate [(lnV₁-lnV₀)/(t₁-t₀)] of 0.42% and an average volume doubling time of 27.15 months. Women had a faster relative growth rate than men. Age and specific mutations did not influence tumor growth. Because of the tumor heterogeneity, we developed an additional cut-off volume of 40 cm³ for surgical intervention.

Conclusions

Tumor heterogeneity and differences in growth kinetics is suggestive of a state of transient tumor dormancy in ccRCCs of VHL patients. The relative growth rate has not been previously described in other studies. Volumetric assessment as an additional parameter for surgical intervention could be a useful clinical tool and needs further investigation.

A Novel Metabolic Signature To Predict the Requirement of Dialysis or Renal Transplantation in Patients with Chronic Kidney Disease

Identification of chronic kidney disease patients at risk of progressing to end-stage renal disease (ESRD) is essential for treatment decision-making and clinical trial design. Here, we explored whether proton nuclear magnetic resonance (NMR) spectroscopy of blood plasma improves the currently best performing kidney failure risk equation, the so-called Tangri score. Our study cohort comprised 4640 participants from the German Chronic Kidney Disease (GCKD) study, of whom 185 (3.99%) progressed over a mean observation time of 3.70 ± 0.88 years to ESRD requiring either dialysis or transplantation. The original four-variable Tangri risk equation yielded a C statistic of 0.863 (95% CI, 0.831-0.900). Upon inclusion of NMR features by state-of-the-art machine learning methods, the C statistic improved to 0.875 (95% CI, 0.850-0.911), thereby outperforming the Tangri score in 94 out of 100 subsampling rounds. Of the 24 NMR features included in the model, creatinine, high-density lipoprotein, valine, acetyl groups of glycoproteins, and Ca²⁺-EDTA carried the highest weights. In conclusion, proton NMR-based plasma fingerprinting improved markedly the detection of patients at risk of developing ESRD, thus enabling enhanced patient treatment.

Genome-Wide Association Studies of Metabolite Concentrations (mGWAS): Relevance for Nephrology

Metabolites are small molecules that are intermediates or products of metabolism, many of which are freely filtered by the kidneys. In addition, the kidneys have a central role in metabolite anabolism and catabolism, as well as in active metabolite reabsorption and/or secretion during tubular passage. This review article illustrates how the coupling of genomics and metabolomics in genome-wide association analyses of metabolites can be used to illuminate mechanisms underlying human metabolism, with a special focus on insights relevant to nephrology. First, genetic susceptibility loci for reduced kidney function and chronic kidney disease (CKD) were reviewed systematically for their associations with metabolite concentrations in metabolomics studies of blood and urine. Second, kidney function and CKD-associated metabolites reported from observational studies were interrogated for metabolite-associated genetic variants to generate and discuss complementary insights. Finally, insights originating from the simultaneous study of both blood and urine or by modeling intermetabolite relationships are summarized. We also discuss methodologic questions related to the study of metabolite concentrations in urine as well as among CKD patients. In summary, genome-wide association analyses of metabolites using metabolite concentrations quantified from blood and/or urine are a promising avenue of research to illuminate physiological and pathophysiological functions of the kidney.

Genome-Wide Association Studies of Metabolites in Patients with CKD Identify Multiple Loci and Illuminate Tubular Transport Mechanisms

Background The kidneys have a central role in the generation, turnover, transport, and excretion of metabolites, and these functions can be altered in CKD. Genetic studies of metabolite concentrations can identify proteins performing these functions.Methods We conducted genome-wide association studies and aggregate rare variant tests of the concentrations of 139 serum metabolites and 41 urine metabolites, as well as their pairwise ratios and fractional excretions in up to 1168 patients with CKD.Results After correction for multiple testing, genome-wide significant associations were detected for 25 serum metabolites, two urine metabolites, and 259 serum and 14 urinary metabolite ratios. These included associations already known from population-based studies. Additional findings included an association for the uremic toxin putrescine and variants upstream of an enzyme catalyzing the oxidative deamination of polyamines (AOC1, P-min=2.4×10^-12), a relatively high carrier frequency (2%) for rare deleterious missense variants in ACADM that are collectively associated with serum ratios of medium-chain acylcarnitines (P-burden=6.6×10^-16), and associations of a common variant in SLC7A9 with several ratios of lysine to neutral amino acids in urine, including the lysine/glutamine ratio (P=2.2×10^-23). The associations of this SLC7A9 variant with ratios of lysine to specific neutral amino acids were much stronger than the association with lysine concentration alone. This finding is consistent with SLC7A9 functioning as an exchanger of urinary cationic amino acids against specific intracellular neutral amino acids at the apical membrane of proximal tubular cells.Conclusions Metabolomic indices of specific kidney functions in genetic studies may provide insight into human renal physiology.

Control procedures and estimators of the false discovery rate and their application in low-dimensional settings: an empirical investigation

Background

When many (up to millions) of statistical tests are conducted in discovery set analyses such as genome-wide association studies (GWAS), approaches controlling family-wise error rate (FWER) or false discovery rate (FDR) are required to reduce the number of false positive decisions. Some methods were specifically developed in the context of high-dimensional settings and partially rely on the estimation of the proportion of true null hypotheses. However, these approaches are also applied in low-dimensional settings such as replication set analyses that might be restricted to a small number of specific hypotheses. The aim of this study was to compare different approaches in low-dimensional settings using (a) real data from the CKDGen Consortium and (b) a simulation study.

Results

In both application and simulation FWER approaches were less powerful compared to FDR control methods, whether a larger number of hypotheses were tested or not. Most powerful was the q-value method. However, the specificity of this method to maintain true null hypotheses was especially decreased when the number of tested hypotheses was small. In this low-dimensional situation, estimation of the proportion of true null hypotheses was biased.

Conclusions

The results highlight the importance of a sizeable data set for a reliable estimation of the proportion of true null hypotheses. Consequently, methods relying on this estimation should only be applied in high-dimensional settings. Furthermore, if the focus lies on testing of a small number of hypotheses such as in replication settings, FWER methods rather than FDR methods should be preferred to maintain high specificity.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2081-x) contains supplementary material, which is available to authorized users.

Did the reporting of prognostic studies of tumour markers improve since the introduction of REMARK guideline? A comparison of reporting in published articles

Although biomarkers are perceived as highly relevant for future clinical practice, few biomarkers reach clinical utility for several reasons. Among them, poor reporting of studies is one of the major problems. To aid improvement, reporting guidelines like REMARK for tumour marker prognostic (TMP) studies were introduced several years ago. The aims of this project were to assess whether reporting quality of TMP-studies improved in comparison to a previously conducted study assessing reporting quality of TMP-studies (PRE-study) and to assess whether articles citing REMARK (citing group) are better reported, in comparison to articles not citing REMARK (not-citing group). For the POST-study, recent articles citing and not citing REMARK (53 each) were identified in selected journals through systematic literature search and evaluated in same way as in the PRE-study. Ten of the 20 items of the REMARK checklist were evaluated and used to define an overall score of reporting quality. The observed overall scores were 53.4% (range: 10%-90%) for the PRE-study, 57.7% (range: 20%-100%) for the not-citing group and 58.1% (range: 30%-100%) for the citing group of the POST-study. While there is no difference between the two groups of the POST-study, the POST-study shows a slight but not relevant improvement in reporting relative to the PRE-study. Not all the articles of the citing group, cited REMARK appropriately. Irrespective of whether REMARK was cited, the overall score was slightly higher for articles published in journals requesting adherence to REMARK than for those published in journals not requesting it: 59.9% versus 51.9%, respectively. Several years after the introduction of REMARK, many key items of TMP-studies are still very poorly reported. A combined effort is needed from authors, editors, reviewers and methodologists to improve the current situation. Good reporting is not just nice to have but is essential for any research to be useful.

Systemic Immunomodulating Therapies for Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: A Systematic Review and Meta-analysis

Importance

Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are rare but severe adverse reactions with high mortality. There is no evidence-based treatment, but various systemic immunomodulating therapies are used.

Objectives

To provide an overview on possible immunomodulating treatments for SJS/TEN and estimate their effects on mortality compared with supportive care.

Data Sources

A literature search was performed in December 2012 for articles published in MEDLINE, MEDLINE Daily, MEDLINE Inprocess, Web of Science, EMBASE, Scopus, and the Cochrane Library (Central) from January 1990 through December 2012, and updated in December 2015, in the English, French, Spanish, and German languages looking for treatment proposals for SJS/TEN. Other sources were screened manually.

Study Selection

Initially, 157 randomized and nonrandomized studies on therapies (systemic immunomodulating therapies or supportive care) for SJS/TEN were selected.

Data Extraction and Synthesis

Relevant data were extracted from articles. Authors were contacted for further information. Finally, 96 studies with sufficient information regarding eligibility and adequate quality scores were considered in the data synthesis. All steps were performed independently by 2 investigators. Meta-analyses on aggregated study data (random-effects model) and individual patient data (IPD) (logistic regression adjusted for confounders) were performed to assess therapeutic efficacy. In the analysis of IPD, 2 regression models, stratified and unstratified by study, were fitted.

Main Outcomes and Measures

Therapy effects on mortality were expressed in terms of odds ratios (ORs) with 95% CIs.

Results

Overall, 96 studies (3248 patients) were included. Applied therapies were supportive care or systemic immunomodulating therapies, including glucocorticosteroids, intravenous immunoglobulins, cyclosporine, plasmapheresis, thalidomide, cyclophosphamide, hemoperfusion, tumor necrosis factor inhibitors, and granulocyte colony-stimulating factors. Glucocorticosteroids were associated with a survival benefit for patients in all 3 analyses but were statistically significant in only one (aggregated data: OR, 0.5; 95%% CI, 0.3-1.01; IPD, unstratified: OR, 0.7; 95% CI, 0.5-0.97; IPD, stratified: OR, 0.8; 95% CI, 0.4-1.3). Despite the low patient size, cyclosporine was associated with a promising significant result in the only feasible analysis of IPD (unstratified model) (OR, 0.1; 95% CI, 0.0-0.4). No beneficial findings were observed for other therapies, including intravenous immunoglobulins.

Conclusions and Relevance

Although all analyses, including the unstratified model, had limitations, glucocorticosteroids and cyclosporine were the most promising systemic immunomodulating therapies for SJS/TEN. Further evaluation in prospective studies is required. However, this work provides a comprehensive overview on proposed systemic immunomodulating treatments for SJS/TEN, which is of great relevance for treating physicians.

Erratum to: Methods for evaluating medical tests and biomarkers

[This corrects the article DOI: 10.1186/s41512-016-0001-y.].

NFAT5 and SLC4A10 Loci Associate with Plasma Osmolality

Disorders of water balance, an excess or deficit of total body water relative to body electrolyte content, are common and ascertained by plasma hypo- or hypernatremia, respectively. We performed a two-stage genome-wide association study meta-analysis on plasma sodium concentration in 45,889 individuals of European descent (stage 1 discovery) and 17,637 additional individuals of European descent (stage 2 replication), and a transethnic meta-analysis of replicated single-nucleotide polymorphisms in 79,506 individuals (63,526 individuals of European descent, 8765 individuals of Asian Indian descent, and 7215 individuals of African descent). In stage 1, we identified eight loci associated with plasma sodium concentration at P<5.0 × 10^-6 Of these, rs9980 at NFAT5 replicated in stage 2 meta-analysis (P=3.1 × 10^-5), with combined stages 1 and 2 genome-wide significance of P=5.6 × 10^-10 Transethnic meta-analysis further supported the association at rs9980 (P=5.9 × 10^-12). Additionally, rs16846053 at SLC4A10 showed nominally, but not genome-wide, significant association in combined stages 1 and 2 meta-analysis (P=6.7 × 10^-8). NFAT5 encodes a ubiquitously expressed transcription factor that coordinates the intracellular response to hypertonic stress but was not previously implicated in the regulation of systemic water balance. SLC4A10 encodes a sodium bicarbonate transporter with a brain-restricted expression pattern, and variant rs16846053 affects a putative intronic NFAT5 DNA binding motif. The lead variants for NFAT5 and SLC4A10 are cis expression quantitative trait loci in tissues of the central nervous system and relevant to transcriptional regulation. Thus, genetic variation in NFAT5 and SLC4A10 expression and function in the central nervous system may affect the regulation of systemic water balance.

7th drug hypersensitivity meeting: part one

Oral Abstracts

O1 Functionally distinct HMGB1 isoforms correlate with physiological processes in drug-induced SJS/TEN

Daniel F. Carr, Wen-Hung Chung, Rosalind E. Jenkiins, Mas Chaponda, Gospel Nwikue, Elena M. Cornejo Castro, Daniel J. Antoine, Munir Pirmohamed

O2 Hypersensitivity reactions to beta-lactams, does the t cell recognition pattern influence the clinical picture?

Natascha Wuillemin, Dolores Dina, Klara K. Eriksson, Daniel Yerly

O3 Specific binding characteristics of HLA alleles associated with nevirapine hypersensitivity

Rebecca Pavlos, Elizabeth Mckinnin, David Ostrov, Bjoern Peters, Soren Buus, David Koelle, Abha Chopra, Craig Rive, Alec Redwood, Susana Restrepo, Austin Bracey, Jing Yuan, Silvana Gaudieri, Mary Carrington, David Haas, Simon Mallal, Elizabeth Phillips

O4 Do we need to measure total ige for the interpretation of analytical results of ImmunoCAP dnd 3gAllergy specific IgE?

Douwe De Boer, Paul Menheere, Chris Nieuwhof, Judith Bons

O5 Neutrophil activation in systemic anaphylaxis: results from the multicentric NASA study

Friederike Jonsson, Luc De Chaisemartin, Vanessa Granger, Caitlin Gillis, Aurelie Gouel, Catherine Neukirch, Fadia Dib, Pascale Roland Nicaise, Dan Longrois, Florence Tubach, Sylvie Martin, Pierre Bruhns, NASA Study Group

O6 Purpuric drug eruptions due to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) for non-small-cell lung cancer (NSCLC): a clinic-pathological study of 32 cases

Kai-Lung Chen, Shu-Ling Liao, Yi-Shuan Sheen, Yung-Tsu Cho, Che-Wen Yang, Jau-Yu Liau, Chia-Yu Chu

Poster presentations: Poster Walk 1—Anaphylaxis (P01–P09)

P1 Anaphylactic reactions during anaesthesia and the perioperative period

Rita Aguiar, Anabela Lopes, Natália Fernandes, Leonor Viegas, M. A. Pereira-Barbosa

P2 Anaphylaxis to chlorhexidine: is there a cross-reactivity to alexidine?

Antonia Bünter, Nisha Gupta, Tatjana Pecaric Petkovic, Nicole Wirth, Werner J. Pichler, Oliver Hausmann

P3 Cefotaxime-induced severe anaphylaxis in a neonate

Mehtap Yazicioglu, Pinar G. Ozdemir, Gokce Ciplak, Ozkan Kaya

P4 Clinical features and diagnosis of anaphylaxis resulting from exposure to chlorhexidine

Peter John Cooke

P5 Drug-induced anaphylaxis: five-year single-center survey

Inês Mota, Ângela Gaspar, Filipe Benito-Garcia, Marta Chambel, Mário Morais-Almeida

P6 Intraoperative severe anaphylactic reaction due to patent blue v dye

Luis Marques, Eva Alcoceba, Silvia Lara

P7 Kounis syndrome in the setting of anaphylaxis to diclofenac

Leonor Carneiro-Leão, Carmen Botelho, Eunice Dias-Castro, Josefina Cernadas

P8 Perioperative anaphylaxis audit: Royal Melbourne Hospital

Katherine Nicholls, William Lay, Olivia Smith, Christine Collins, Gary Unglik, Kymble Spriggs, Priscilla Auyeung, Jeremy McComish, Jo A. Douglass

P9 Recurrent peri-operative anaphylaxis: a perfect storm

Jonny G. Peter, Paul Potter

Poster Walk 2: DH regions and patient groups (P10–P19)

P10 A rare presentation of amoxicillin allergy in a young child

Fabrícia Carolino, Eunice Dias De Castro, Josefina R. Cernadas

P11 Adverse drug reactions in children: antibiotics or virus?

Ana Sofia Moreira, Carmo Abreu, Eva Gomes

P12 Allergic reactions in invasive medical procedures

Bárbara Kong Cardoso, Elza Tomaz, Sara Correia, Filipe Inácio

P13 Antibiotic allergy in children: room for improvement

Annabelle Arnold, Natasha Bear, Kristina Rueter, Grace Gong, Michael O’Sullivan, Saravanan Muthusamy, Valerie Noble, Michaela Lucas

P14 Drug hypersensitivity reactions in children and results of diagnostic evaluation

Neringa Buterleviciute, Odilija Rudzeviciene

P15 Nonimmediate cutaneous drug reactions in children: are skin tests required?

Ana Sofia Moreira, Carmo Abreu, Eva Gomes

P16 Pediatric patients with a history of penicillin allergy and a positive penicillin skin test may not be at an increased risk for multiple drug allergies

Sara May, Thanai Pongdee, Miguel Park

P17 Proved hypersensitivity to drugs according data of Vilnius University Hospital Santariskiu Klinikos

Linas Griguola, Arturas Vinikovas, Simona Kašinskaite, Violeta Kvedariene

P18 Self-reported prevalence of drug hypersensitivity reactions among students in Celal Bayar University, Turkey

Ayse Aktas, Suheyla Rahman, Huseyin Elbi, Beyhan Cengiz Ozyurt

P19 Severe drug hypersensitivity reactions in pediatric age

Ozlem Cavkaytar, Betul Karaatmaca, Pinar Gur Cetinkaya, Saliha Esenboga, Umit M. Sahiner, Bulent E. Sekerel, Ozge Soyer

Poster Walk 3: Desensitisation (P20–P28)

P20 A protocol for desensitisation to valaciclovir

Celia Zubrinich, Bianca Tong, Mittal Patel, Michelle Giles, Robyn O’Hehir, Robert Puy

P21 A rare case of desensitization to modafinil

Josefina Cernadas, Luís Amaral, Fabrícia Carolino

P22 A sixteen-day desensitization protocol in delayed type hypersensitivity reactions to oral drugs

Semra Demir, Asli Gelincik, Muge Olgac, Raif Caskun, Derya Unal, Bahauddin Colakoglu, Suna Buyukozturk

P23 Desensitization to intravenous etoposide using a 12 and a 13-step protocol. Two cases report

Olga Vega Matute, Amalia Bernad, Gabriel Gastaminza, Roselle Madamba, Carlos Lacasa, M. J. Goikoetxea, Carmen D’Amelio, Jose Rifón, Nicolas Martínez, Marta Ferrer

P24 Drug desensitisation in oncology: the experience of an immunoallergology department for 5 years

Carmelita Ribeiro, Emília Faria, Cristina Frutuoso, Anabela Barros, Rosário Lebre, Alice Pego, Ana Todo Bom

P25 Filgrastim anaphylaxis: a successful desensitization protocol

Luis Amaral, Josefina Cernadas

P26 Galsulfase hypersensitivity and desensitization of a mucopolysaccharidosis VI patient

Luis Felipe Ensina, Carolina Aranda, Ines Camelo Nunes, Ana Maria Martins, Dirceu Solé

P27 Rapid drug desensitization with biologicals: one-center experience with four biologicals

Sevim Bavbek, Resat Kendirlinan, Pamir Çerçi, Seda Tutluer, Sadan Soyyigit, Zeynep Çelebi Sözener, Ömür Aydin, Reyhan Gümüsburun

P28 Successful desensitization to a high dose of methotrexate in a delayed type hypersensitivity reaction

Josefina Cernadas, Leonor Carneiro-Leão, Fabrícia Carolino, Marta Almeida

Poster Walk 4: SJS (P29–P38)

P29 Assessment of impact of infection on drug-induced severe cutaneous adverse reactions and rhabdomyolysis using the Japanese adverse drug event report database

Kimie Sai, Takuya Imatoh, Ryosuke Nakamura, Chisato Fukazawa, Yasushi Hinomura, Yoshiro Saito

P30 Characterization of erythema multiforme and severe cutaneous adverse reactions hospitalizations

Bernardo Sousa-Pinto, Cláudia Correia, Lídia Gomes, Sara Gil-Mata, Luís Araújo, Luís Delgado

P31 Effects of infection on incidence/severity of SJS/TEN and myopathy in Japanese cases analyzed by voluntary case reports

Ryosuke Nakamura, Kimie Sai, Takuya Imatoh, Yoshimi Okamoto-Uchida, Koji Kajinami, Kayoko Matsunaga, Michiko Aihara, Yoshiro Saito

P32 Efficacy of tumor necrosis factor—a antagonists in Stevens–Johnson syndrome and toxic epidermal necrolysis: a randomized controlled trial and immunosuppressive effects evaluation

Chuang-Wei Wang, Shih-Chi Su, Shuen-Iu Hung, Hsin-Chun Ho, Chih-Hsun Yang, Wen-Hung Chung

P33 Evolution of drug causality in Stevens–Johnson syndrome and toxic epidermal necrolysis in Europe: analysis of 10 years RegiSCAR-Study

Maren Paulmann, Ariane Dunant, Maja Mockenhaupt, Peggy Sekula, Martin Schumacher, Sylvia Kardaun, Luigi Naldi, Teresa Bellón, Daniel Creamer, Cynthia Haddad, Bruno Sassolas, Bénédicte Lebrun-Vignes, Laurence Valeyrie-Allanore, Jean-Claude Roujeau

P34 Long-term sequelae in patients with Stevens–Johnson syndrome and toxic epidermal necrolysis: a 5-year analysis

Maren Paulmann, Carmen Kremmler, Peggy Sekula, Laurence Valeyrie-Allanore, Luigi Naldi, Sylvia Kardaun, Maja Mockenhaupt

P35 Major emotional complications and decreased health related quality of life among survivors of Stevens–Johnson syndrome and toxic epidermal necrolysis

Roni P. Dodiuk-Gad, Cristina Olteanu, Anthony Feinstein, Rena Hashimoto, Raed Alhusayen, Sonia Whyte-Croasdaile, Yaron Finkelstein, Marjorie Burnett, Shachar Sade, Robert Cartotto, Marc Jeschke, Neil H. Shear

P36 Retrospective analysis of Stevens–Johnson syndrome and toxic epidermal necrolysis in Japanese patients: treatment and outcome

Naoko Takamura, Yumiko Yamane, Setsuko Matsukura, Kazuko Nakamura, Yuko Watanabe, Yukie Yamaguchi, Takeshi Kambara, Zenro Ikezawa, Michiko Aihara

P37 Severe physical complications among survivors of Stevens–Johnson syndrome and toxic epidermal necrolysis

Roni P. Dodiuk-Gad, Cristina Olteanu, Rena Hashimoto, Hall Chew, Raed Alhusayen, Sonia Whyte-Croasdaile, Yaron Finkelstein, Marjorie Burnett, Shachar Sade, Robert Cartotto, Marc Jeschke, Neil H. Shear

P38 Stevens–Johnson syndrome/toxic epidermal necrolysis combined with haemophagocytic lymphohistiocytosis: a case report

Brittany Knezevic, Una Nic Ionmhain, Allison Barraclough, Michaela Lucas, Matthew Anstey

Poster Walk 5: Other organs/unexpected immune reactions (P39–P47)

P39 A case report of patient with anti-tuberculosis drug-related severe liver failure

Toru Usui, Xiaoli Meng, John Farrell, Paul Whitaker, John Watson, Neil French, Kevin Park, Dean Naisbitt

P40 Acute interstitial nephritis induced by ibuprofen

Ana Castro Neves, Susana Cadinha, Ana Moreira, J. P. Moreira Da Silva

P41 Cetuximab induced acneiform rash—two case reports

Daniela Ledic Drvar, Sandra Jerkovic Gulin, Suzana Ljubojevic Hadzavdic, Romana Ceovic

P42 Enteropathy associated with losartan

Ana Montoro De Francisco, Talía De Vicente Jiménez, Amelia García Luque, Natalia Rosado David, José Mª Mateos Galván

P43 Granuloma annulare after therapy with canakinumab

Razvigor Darlenski

P44 Hypersensitivity eosinophilic myocarditis or acute coronary syndrome? Case report

Dario Gulin, Jozica Sikic, Jasna Cerkez Habek, Sandra Jerkovic Gulin, Edvard Galic

P45 Piperacillin-induced immune haemolytic anaemia: a severe and frequent complication of antibiotic treatment in patients with cystic fibrosis

Philip Specht, Doris Staab, Beate Mayer, Jobst Roehmel

P46 Progesterone triggered pemphigus foliaceus: case report

Sandra Jerkovic Gulin, Caius Solovan, Anca Chiriac

P47 Ramipril: triggered generalized pustular psoriasis

Paola Djurinec, Kresimir Kostovic, Mirna Bradamante, Sandra Jerkovic Gulin, Romana Ceovic

Poster Walk 6: NSAIDs (P48–P56)

P48 Aspirin desensitization in cardiovascular disease—Portuguese experience

Jose Pedro Almeida, Joana Caiado, Elisa Pedro, Pedro Canas Da Silva, Manuel Pereira Barbosa

P49 Asthma and/or rhinitis to NSAIDs with good tolerance to ASA

Gador Bogas, Natalia Blanca-López, Diana Pérez-Alzate, Inmaculada Doña, José Augusto Agúndez, Elena García-Martín, José Antonio Cornejo-García, Cristobalina Mayorga, María José Torres, Gabriela Canto, Miguel Blanca

P50 Clinical characteristics of 196 patients with non-steroidal anti-inflammatory drug (NSAIDs) hypersensitivity

Sengül Aksakal, Aytül Zerrin Sin, Zeynep Peker Koç, Fatma Düsünür Günsen, Ömür Ardeniz, Emine Nihal Mete Gökmen, Okan Gülbahar, Ali Kokuludag

P51 Development of immediate hypersensitivity to several NSAIDs maintaining good tolerance to ASA

Natalia Pérez-Sánchez, Natalia Blanca-López, Diana Pérez-Alzate, Gador Bogas, Inmaculada Doña, María Salas, María José Torres, Miguel Blanca, Gabriela Canto

P52 Diagnosis of hypersensitivity reactions to paracetamol in a large series of cases

Inmaculada Doña, Maria Salas, Francisca Gomez, Natalia Blanca-Lopez, Diana Perez-Alzate, Gador Bogas, Esther Barrionuevo, Maria Jose Torres, Inmaculada Andreu, Miguel Ángel Miranda, Gabriela Canto, Miguel Blanca

P53 Hypersensitivity to paracetamol according to the new classification of hypersensitivity to NSAIDs

Gabija Didžiokaite, Olesia Gaidej, Simona Kašinskaite, Violeta Kvedariene

P54 Ibuprofen and other aryl propionic derivates can induce immediate selective hypersensitivity responses

Diana Perez-Alzate, Natalia Blanca-López, Maria Isabel Garcimartin, Inmaculada Doña, Maria Luisa Somoza, Cristobalina Mayorga, Maria Jose Torres, Gador Bojas, Jose Antonio Cornejo-Garcia, Maria Gabriela Canto, Miguel Blanca

P55 Subjects developing immediate responses to several NSAIDs can be selective with good tolerance to ASA

Natalia Blanca-Lopez, Diana Pérez-Alzate, Francisco Javier Ruano Perez, Inmaculada Doña, Maria Luisa Somoza, Inmaculada Andreu, Miguel Angel Miranda, Cristobalina Mayorga, Maria Jose Torres, Jose Antonio Cornejo-Garcia, Miguel Blanca, Maria Gabriela Canto

P56 Utility of low-dose oral aspirin challenges for diagnosis of aspirin exacerbated respiratory disease

Elina Jerschow, Teresa Pelletier, Zhen Ren, Golda Hudes, Marek Sanak, Esperanza Morales, Victor Schuster, Simon D. Spivack, David Rosenstreich

Poster Walk 7: NSAID 2 (P57–P65)

P57 Alternate regulation of cyclooxygenase-2 (COX-2) MRNA expression may predispose patients to aspirin-induced exacerbations

Renato Erzen, Mira Silar, Nissera Bajrovic, Matija Rijavec, Mihaela Zidarn, Peter Korosec

P58 Anaphylaxis to diclofenac: what about the underlying mechanism?

Leonor Carneiro-Leão, Fabrícia Carolino, Luís Amaral, Carmen Botelho, Eunice Dias-Castro, Josefina Cernadas

P59 COX-2 inhibitors: are they always a safe alternative in hypersensitivity to nonsteroidal anti-inflammatory drugs?

Luis Amaral, Fabricia Carolino, Eunice Castro, Josefina Cernadas

P60 Management of patients with history of NSAIDs reactions prior to coronary angioplasty

Mona Al-Ahmad, Tito Rodriguez

P61 Oral drug challenge with non-steroidal anti-inflammatory drug under spirometric control: clinical series of 110 patients

João Pedro Azevedo, Emília Faria, Beatriz Tavares, Frederico Regateiro, Ana Todo-Bom

P62 Prevalence and incidence of analgesic hypersensitivity reactions in Colombia

Pablo Andrés Miranda, Bautista De La Cruz Hoyos

P63 Recent endoscopic sinus surgery lessens reactions during aspirin challenge in patients with aspirin exacerbated respiratory disease

Teresa Pelletier, Waleed Abuzeid, Nadeem Akbar, Marc Gibber, Marvin Fried, Weiguo Han, Taha Keskin, Robert Tamayev, Golda Hudes, Simon D. Spivack, David Rosenstreich, Elina Jerschow

P64 Safe use of imidazole salycilate in a case of multiple NSAIDs induced urticaria-angioedema

Elisa Boni, Marina Russello, Marina Mauro

P65 Selective hypersensitivity reactions to ibuprofen—seven years experience

Marta Ferreira Neto

Poster Walk 8: Epidemiological methods (P66–P72)

P66 Allopurinol hypersensitivity: a 7-year review

Lise Brosseron, Daniela Malheiro, Susana Cadinha, Patrícia Barreira, J. P. Moreira Da Silva

P67 Antibiotic allergy labelling is associated with increased hospital readmission rates in Australia

Brittany Knezevic, Dustin Sprigg, Michelle Trevenen, Jason Seet, Jason Trubiano, William Smith, Yogesh Jeelall, Sandra Vale, Richard Loh, Andrew Mclean-Tooke, Michaela Lucas

P68 Experts’ opinions on severe cutaneous adverse drug reactions-report of a survey from the 9th international congress on cutaneous adverse drug reactions 2015

Roni P. Dodiuk-Gad, Cristina Olteanu, Wen-Hung Chung, Neil H. Shear

P69 HLA-A*31-positive AGEP with carbamazepine use and other severe cutaneous adverse drug reactions (SCARs) detected by electronic medical records screening

Sabine Müller, Ursula Amstutz, Lukas Jörg, Nikhil Yawalkar, Stephan Krähenbühl

P70 Patients with suspected drug allergy: a specific psychological profile?

Eunice Dias-Castro, Ana Leblanc, Laura Ribeiro, Josefina R. Cernadas

P71 Use of an electronic device and a computerized mathematic algorithm to detect the allergic drug reactions through the analysis of heart rate variability

Arantza Vega, Raquel Gutierrez Rivas, Ana Alonso, Juan Maria Beitia, Belén Mateo, Remedios Cárdenas, Juan Jesus Garcia-Dominguez

P72 Variation in ERAP influences risk for HLA-B*57:01 positive abacavir hypersensitivity

Rebecca Pavlos, Kaija Strautins, Ian James, Simon Mallal, Alec Redwood, Elizabeth Phillips

Poster Walk 9: DRESS/AGEP (P73–P81)

P73 A clinical case of DRESS syndrome in a child after administration of amoxicillin-clavulanic acid

Rita Aguiar, Anabela Lopes, Ana Neves, Maria Do Céu Machado, M. A. Pereira-Barbosa

P74 Acute generalized exanthematous pustulosis (AGEP) induced by mesalazine, reliable and oftenly used drug to treat inflammatory bowel disease

Ceyda Tunakan Dalgiç, Emine Nihal Mete Gökmen, Fatma Düsünür Günsen, Gökten Bulut, Fatma Ömür Ardeniz, Okan Gülbahar, Ali Kokuludag, Aytül Zerrin Sin

P75 Changes of blood plasmacytoid dendritic cells, myeloid dendritic cells, and basophils during the acute stage of drug reaction with eosinophilia and systemic symptoms (DRESS) and other drug eruptions

Shao-Hsuan Hsu, Yung-Tsu Cho, Che-Wen Yang, Kai-Lung Chen, Chia-Yu Chu

P76 Characterization of isoniazid/rifampicin-specific t-cell responses in patients with DRESS syndrome

Young-Min Ye, Gyu-Young Hur, Hae-Sim Park, Seung-Hyun Kim

P77 DRESS syndrome secondary to sulfasalazine with delayed TEN: a case presentation

Syed Ali, Michaela Lucas, Peter N. Hollingsworth, Andrew P. C. Mclean-Tooke

P78 Drug rash with eosinophilia and systemic symptoms (DRESS) features according to the culprit drug

Zohra Chadly, Nadia Ben Fredj, Karim Aouam, Haifa Ben Romdhane, Naceur A. Boughattas, Amel Chaabane

P79 Drug reaction with eosinophilia and systemic symptoms induced by allopurinol: not always easy to diagnose

Marina Lluncor Salazar, Beatriz Pola, Ana Fiandor, Teresa Bellón, Elena Ramírez, Javier Domínguez Ortega, Santiago Quirce, Rosario Cabañas

P80 Drug reaction with eosinophilia and systemic symptoms syndrome induced by two drugs simultaneously: a case report

Krasimira Baynova, Marina Labella, Manuel Prados

P81 The drug reaction with eosinophilia and systemic symptoms (DRESS) induced by the second-line antituberculosis drugs and Epstein–Barr virus infection

Agne Ramonaite, Ieva Bajoriuniene, Brigita Sitkauskiene, Raimundas Sakalauskas

Poster Walk 10: Miscellaneous drug hypersensitivity (P82–P91)

P82 A case of cycloserine-induced lichenoid drug eruption confirmed with a lymphocatye transformation test

Jae-Woo Kwon, Shinyoung Park

P83 Allergic reaction to topical eye drops: 5 years’ retrospective study in a drug allergy unit

Diana Silva, Leonor Carneiro Leão, Fabricia Carolino, Eunice Castro, Josefina Cernadas

P84 Allergy to heparins

Diana Perez-Alzate, Natalia Blanca-López, Maria Luisa Somoza Alvarez, Maria Garcimartin, Maria Vazquez De La Torre, Francisco Javier Ruano Pérez, Elisa Haroun, Gabriela Canto Diez

P85 Allopurinol-induced adverse drug reactions

Katinka Ónodi-Nagy, Ágnes Kinyó, Lajos Kemény, Zsuzsanna Bata-Csörgo

P86 Analysis of a population with immediate hypersensitivity to corticosteroids: an 11 year review

Joana Sofia Pita, Emília Faria, Rosa Anita Fernandes, Ana Moura, Nuno Sousa, Carmelita Ribeiro, Carlos Loureiro, Ana Todo Bom

P87 Anaphylaxis against mivacurium in a 12-months old boy at first-time exposure

Wolfgang Pfützner

P88 Antihistamine-exacerbated chronic spontaneous urticaria: a paradox?

Nadine Marrouche, Clive Grattan

P89 Anti-osteoporotic agents-induced cutaneous adverse drug reactions in Asians

Yu-En Chen, Chun-Bing Chen, Wen-Hung Chung, Yu-Ping Hsiao, Chia-Yu Chu

P90 Diagnosis of allergic reactions to eye drops

Maria Vazquez De La Torre, Natalia Blanca-Lopez, Diana Perez-Alzate, Maria Isabel Garcimartin, Francisco Javier Ruano, Maria Luisa Somoza, Elisa Haroun, Gabriela Canto

P91 Diagnostic approach in suspected hypersensitivity reactions to corticosteroids

Fabrícia Carolino, Eunice Dias De Castro, Josefina R. Cernadas

The case-crossover design via penalized regression

BACKGROUND

The case-crossover design is an attractive alternative to the classical case-control design which can be used to study the onset of acute events if the risk factors of interest vary in time. By comparing exposures within cases at different time periods, the case-crossover design does not rely on control subjects which can be difficult to acquire. However, using the standard method of maximum likelihood, resulting risk estimates can be heavily biased when the prevalence to risk factors is very low (or very high).

METHODS

To overcome the problem of low risk factor prevalences, penalized conditional logistic regression via the lasso (least absolute shrinkage and selection operator) has been proposed in the literature as well as related methods such as the Firth correction. We apply and compare several penalized regression approaches in the context of a case-crossover analysis of the European Study of Severe Cutaneous Adverse Reactions (EuroSCAR; 1997-2001).

RESULTS

Out of 30 drugs, standard methods only correctly classified 17 drugs (including some highly implausible risk estimates), while penalized methods correctly classified 22 drugs.

CONCLUSION

Penalized methods generally yield better risk classifications and much more plausible risk estimates for the EuroSCAR study than standard methods. As these novel techniques can be easily implemented using available R packages, we encourage routine use of penalized conditional logistic regression for case-crossover data.

Assessment of the extent of unpublished studies in prognostic factor research: a systematic review of p53 immunohistochemistry in bladder cancer as an example

OBJECTIVES

When study groups fail to publish their results, a subsequent systematic review may come to incorrect conclusions when combining information only from published studies. p53 expression measured by immunohistochemistry is a potential prognostic factor in bladder cancer. Although numerous studies have been conducted, its role is still under debate. The assumption that unpublished studies too harbour evidence on this research topic leads to the question about the attributable effect when adding this information and comparing it with published data. Thus, the aim was to identify published and unpublished studies and to explore their differences potentially affecting the conclusion on its function as a prognostic biomarker.

DESIGN

Systematic review of published and unpublished studies assessing p53 in bladder cancer in Germany between 1993 and 2007.

RESULTS

The systematic search revealed 16 studies of which 11 (69%) have been published and 5 (31%) have not. Key reason for not publishing the results was a loss of interest of the investigators. There were no obviously larger differences between published and unpublished studies. However, a meaningful meta-analysis was not possible mainly due to the poor (ie, incomplete) reporting of study results.

CONCLUSIONS

Within this well-defined population of studies, we could provide empirical evidence for the failure of study groups to publish their results that was mainly caused by loss of interest. This fact may be coresponsible for the role of p53 as a prognostic factor still being unclear. We consider p53 and the restriction to studies in Germany as a specific example, but the critical issues are probably similar for other prognostic factors and other countries.

Mendelian Randomization as an Approach to Assess Causality Using Observational Data

Mendelian randomization refers to an analytic approach to assess the causality of an observed association between a modifiable exposure or risk factor and a clinically relevant outcome. It presents a valuable tool, especially when randomized controlled trials to examine causality are not feasible and observational studies provide biased associations because of confounding or reverse causality. These issues are addressed by using genetic variants as instrumental variables for the tested exposure: the alleles of this exposure-associated genetic variant are randomly allocated and not subject to reverse causation. This, together with the wide availability of published genetic associations to screen for suitable genetic instrumental variables make Mendelian randomization a time- and cost-efficient approach and contribute to its increasing popularity for assessing and screening for potentially causal associations. An observed association between the genetic instrumental variable and the outcome supports the hypothesis that the exposure in question is causally related to the outcome. This review provides an overview of the Mendelian randomization method, addresses assumptions and implications, and includes illustrative examples. We also discuss special issues in nephrology, such as inverse risk factor associations in advanced disease, and outline opportunities to design Mendelian randomization studies around kidney function and disease.

Genetic risk variants for membranous nephropathy: extension of and association with other chronic kidney disease aetiologies

Background

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults. Previous genome-wide association studies (GWAS) of 300 000 genotyped variants identified MN-associated loci at HLA-DQA1 and PLA2R1.

Methods

We used a combined approach of genotype imputation, GWAS, human leucocyte antigen (HLA) imputation and extension to other aetiologies of chronic kidney disease (CKD) to investigate genetic MN risk variants more comprehensively. GWAS using 9 million high-quality imputed genotypes and classical HLA alleles were conducted for 323 MN European-ancestry cases and 345 controls. Additionally, 4960 patients with different CKD aetiologies in the German Chronic Kidney Disease (GCKD) study were genotyped for risk variants at HLA-DQA1 and PLA2R1.

Results

In GWAS, lead variants in known loci [rs9272729, HLA-DQA1, odds ratio (OR) = 7.3 per risk allele, P = 5.9 × 10^-27 and rs17830558, PLA2R1, OR = 2.2, P = 1.9 × 10^-8] were significantly associated with MN. No novel signals emerged in GWAS of X-chromosomal variants or in sex-specific analyses. Classical HLA alleles (DRB1*0301-DQA1*0501-DQB1*0201 haplotype) were associated with MN but provided little additional information beyond rs9272729. Associations were replicated in 137 GCKD patients with MN (HLA-DQA1: P = 6.4 × 10^-24; PLA2R1: P = 5.0 × 10^-4). MN risk increased steeply for patients with high-risk genotype combinations (OR > 79). While genetic variation in PLA2R1 exclusively associated with MN across 19 CKD aetiologies, the HLA-DQA1 risk allele was also associated with lupus nephritis (P = 2.8 × 10^-6), type 1 diabetic nephropathy (P = 6.9 × 10^-5) and focal segmental glomerulosclerosis (P = 5.1 × 10^-5), but not with immunoglobulin A nephropathy.

Conclusions

PLA2R1 and HLA-DQA1 are the predominant risk loci for MN detected by GWAS. While HLA-DQA1 risk variants show an association with other CKD aetiologies, PLA2R1 variants are specific to MN.

A Metabolome-Wide Association Study of Kidney Function and Disease in the General Population

Small molecules are extensively metabolized and cleared by the kidney. Changes in serum metabolite concentrations may result from impaired kidney function and can be used to estimate filtration (e.g., the established marker creatinine) or may precede and potentially contribute to CKD development. Here, we applied a nontargeted metabolomics approach using gas and liquid chromatography coupled to mass spectrometry to quantify 493 small molecules in human serum. The associations of these molecules with GFR estimated on the basis of creatinine (eGFRcr) and cystatin C levels were assessed in ≤1735 participants in the KORA F4 study, followed by replication in 1164 individuals in the TwinsUK registry. After correction for multiple testing, 54 replicated metabolites significantly associated with eGFRcr, and six of these showed pairwise correlation (r≥0.50) with established kidney function measures: C-mannosyltryptophan, pseudouridine, N-acetylalanine, erythronate, myo-inositol, and N-acetylcarnosine. Higher C-mannosyltryptophan, pseudouridine, and O-sulfo-L-tyrosine concentrations associated with incident CKD (eGFRcr <60 ml/min per 1.73 m(2)) in the KORA F4 study. In contrast with serum creatinine, C-mannosyltryptophan and pseudouridine concentrations showed little dependence on sex. Furthermore, correlation with measured GFR in 200 participants in the AASK study was 0.78 for both C-mannosyltryptophan and pseudouridine concentration, and highly significant associations of both metabolites with incident ESRD disappeared upon adjustment for measured GFR. Thus, these molecules may be alternative or complementary markers of kidney function. In conclusion, our study provides a comprehensive list of kidney function-associated metabolites and highlights potential novel filtration markers that may help to improve the estimation of GFR.