Risk Prediction Models for Renal Function Decline After Cardiac Surgery Within Different Preoperative Glomerular Filtration Rate Strata

BACKGROUND

Our goal was to create a simple risk-prediction model for renal function decline after cardiac surgery to help focus renal follow-up efforts on patients most likely to benefit.

METHODS AND RESULTS

This single-center retrospective cohort study enrolled 24 904 patients who underwent cardiac surgery from 2012 to 2019 at Fuwai Hospital, Beijing, China. An estimated glomerular filtration rate (eGFR) reduction of ≥30% 3 months after surgery was considered evidence of renal function decline. Relative to patients with eGFR 60 to 89 mL/min per 1.73 m2 (4.5% [531/11733]), those with eGFR ≥90 mL/min per 1.73 m2 (10.9% [1200/11042]) had a higher risk of renal function decline, whereas those with eGFR ≤59 mL/min per 1.73 m2 (5.8% [124/2129]) did not. Each eGFR stratum had a different strongest contributor to renal function decline: increased baseline eGFR levels for patients with eGFR ≥90 mL/min per 1.73 m2, transfusion of any blood type for patients with eGFR 60 to 89 mL/min per 1.73 m2, and no recovery of renal function at discharge for patients with eGFR ≤59 mL/min per 1.73 m2. Different nomograms were established for the different eGFR strata, which yielded a corrected C-index value of 0.752 for eGFR ≥90 mL/min per 1.73 m2, 0.725 for eGFR 60-89 mL/min per 1.73 m2 and 0.791 for eGFR ≤59 mL/min per 1.73 m2.

CONCLUSIONS

Predictors of renal function decline over the follow-up showed marked differences across the eGFR strata. The nomograms incorporated a small number of variables that are readily available in the routine cardiac surgical setting and can be used to predict renal function decline in patients stratified by baseline eGFR.

Chronic Interstitial Nephritis in Agricultural Communities: Observational and Mechanistic Evidence Supporting the Role of Nephrotoxic Agrochemicals

Chronic interstitial nephritis in agricultural communities (CINAC) is an epidemic of kidney disease affecting specific tropical and subtropical regions worldwide and is characterized by progressive CKD in the absence of traditional risk factors, such as hypertension and diabetes. CINAC prevalence is higher among young, male agricultural workers, but it also affects women, children, and nonagricultural workers in affected areas. Biopsies from patients with CINAC across regions commonly demonstrate tubular injury with lysosomal aggregates, tubulointerstitial inflammation, and fibrosis and variable glomerular changes. Each endemic area holds environmental risk factors and patient/genetic milieus, resulting in uncertainty about the cause(s) of the disease. Currently, there is no specific treatment available for CINAC. We highlight survey findings of Houston-based migrant workers with CINAC and draw similarities between kidney injury phenotype of patients with CINAC and mice treated chronically with paraquat, an herbicide used worldwide. We propose potential pathways and mechanisms for kidney injury in patients with CINAC, which may offer clues for potential therapies.

Efficacy of Voclosporin in Proliferative Lupus Nephritis with High Levels of Proteinuria

BACKGROUND

In a phase 3 study of adults with active lupus nephritis, addition of voclosporin to mycophenolate mofetil (MMF) and low-dose glucocorticoids led to significant improvements in the proportion of participants achieving complete and partial renal response as well as sustained reduction in proteinuria. This analysis examined the efficacy and safety of voclosporin in a subgroup of the phase 3 study with proliferative lupus nephritis and high levels of proteinuria.

METHODS

Participants were randomized to oral voclosporin (23.7 mg twice daily) or placebo for 12 months; all participants received MMF and low-dose glucocorticoids. This analysis includes participants with class III or IV (±class V) lupus nephritis and baseline urine protein-creatinine ratio (UPCR) ≥3 g/g. Efficacy end points included complete renal response (UPCR ≤0.5 g/g with stable eGFR, low-dose glucocorticoids, and no rescue medication), partial renal response (≥50% reduction from baseline UPCR), and UPCR over time. Safety outcomes were also assessed.

RESULTS

A total of 148 participants were in the voclosporin ( n =76) and control ( n =72) arms. At 12 months, 34% and 11% of participants in the voclosporin and control arms, respectively, achieved a complete renal response (odds ratio, 4.43; 95% confidence interval [CI], 1.78 to >9.99; P = 0.001). A partial renal response was achieved by 65% of the voclosporin arm and 51% of the control arm at 12 months (odds ratio, 1.60; 95% CI, 0.8 to 3.20; P = 0.18). More voclosporin- than control-treated participants achieved UPCR ≤0.5 g/g (51% versus 26%), and voclosporin-treated participants met this end point significantly earlier (hazard ratio, 2.07; 95% CI, 1.19 to 3.60; P = 0.01). The incidence of adverse events was similar between the arms; mean eGFR values remained stable and within normal range in both arms.

CONCLUSIONS

Addition of voclosporin to MMF and low-dose glucocorticoids resulted in a significantly higher proportion of participants with proliferative lupus nephritis achieving complete and partial renal responses as well as earlier reductions in proteinuria, with no evidence of worsening kidney function.

Validation of eGFR for Detecting Associations Between Serum Protein Biomarkers and Subsequent GFR Decline

SIGNIFICANCE STATEMENT

eGFR from creatinine, cystatin C, or both has been primarily used in search of biomarkers for GFR decline. Whether the relationships between biomarkers and eGFR decline are similar to associations with measured GFR (mGFR) decline has not been investigated. This study revealed that some biomarkers showed statistically significant different associations with eGFR decline compared with mGFR decline, particularly for eGFR from cystatin C. The findings indicate that non-GFR-related factors, such as age, sex, and body mass index, influence the relationship between biomarkers and eGFR decline. Therefore, the results of biomarker studies using eGFR, particularly eGFRcys, should be interpreted with caution and perhaps validated with mGFR.

BACKGROUND

Several serum protein biomarkers have been proposed as risk factors for GFR decline using eGFR from creatinine or cystatin C. We investigated whether eGFR can be used as a surrogate end point for measured GFR (mGFR) when searching for biomarkers associated with GFR decline.

METHODS

In the Renal Iohexol Clearance Survey, GFR was measured with plasma iohexol clearance in 1627 individuals without diabetes, kidney, or cardiovascular disease at baseline. After 11 years of follow-up, 1409 participants had one or more follow-up GFR measurements. Using logistic regression and interval-censored Cox regression, we analyzed the association between baseline levels of 12 serum protein biomarkers with the risk of accelerated GFR decline and incident CKD for both mGFR and eGFR.

RESULTS

Several biomarkers exhibited different associations with eGFR decline compared with their association with mGFR decline. More biomarkers showed different associations with eGFRcys decline than with eGFRcre decline. Most of the different associations of eGFR decline versus mGFR decline remained statistically significant after adjustment for age, sex, and body mass index, but several were attenuated and not significant after adjusting for the corresponding baseline mGFR or eGFR.

CONCLUSIONS

In studies of some serum protein biomarkers, eGFR decline may not be an appropriate surrogate outcome for mGFR decline. Although the differences from mGFR decline are attenuated by adjustment for confounding factors in most cases, some persist. Therefore, proposed biomarkers from studies using eGFR should preferably be validated with mGFR.

Natural course and determinants of short-term kidney function decline in hereditary transthyretin amyloidosis: a French observational study

Data regarding renal involvement in patients with hereditary transthyretin (ATTRv) amyloidosis are scarce and the natural course of chronic kidney disease (CKD) in this population remains unclear. This observational study, including adult patients diagnosed with ATTRv amyloidosis at the French Reference Centre for Cardiac Amyloidosis, investigated renal function outcome and its determinants. Multivariable logistic regression models identified factors associated with CKD at baseline. Determinants of the change in estimated glomerular filtration rate (eGFR) over 24 months of follow-up were assessed with a multivariable linear mixed-effects model. In total, 232 patients (78 women [34%], mean age: 64 years) with ATTRv amyloidosis were classified on the basis of their TTR variants: ATTRV122I (37%), ATTRV30M (29%), and other variants (34%). Median baseline eGFR was 78 ml/min/1.73 m². Seventy-two patients (31%) had an eGFR below 60 ml/min/1.73m² and 27/137 patients (20%) had significant proteinuria (urine protein/creatinine ratio ≥30 mg/mmol). Renal biopsy, performed in four cases, found typical Congo red-positive and TTR-labelled amyloid deposits in all cases. Older age (OR 1.07, p < .001) and a prior history of hypertension (OR 2.09, p = .04) were associated with a higher prevalence of CKD at baseline, whereas higher left ventricular global longitudinal strain (LVGLS) (OR 0.83, p < .001) was associated with a lower prevalence. The estimated change in eGFR was -7.12 [-9.61, -4.63] and -8.21 [-10.81, -5.60] ml/min/1.73 m² after 12 and 24 months of follow-up, respectively. eGFR decline was independently associated with older age ((67-74], coefficient= -14.35 mL/min/1.73 m², p < .01, >74, coefficient = -22.93 mL/min/1.73 m², p < .001, versus <56), ATTRV122I (coefficient = -17.17 mL/min/1.73m², p < .01, versus ATTRV30M) and LVGLS (coefficient = 1.22, p < .01). These data suggest that CKD is a common finding in patients with ATTRv amyloidosis, and that eGFR decline is rapid during the first year of evaluation. Older age, lower LVGLS and ATTRV122I were associated with a worse renal outcome. Further studies are now needed to evaluate effects of new targeted therapies on long term renal function.

Association between sleep duration and quality with rapid kidney function decline and development of chronic kidney diseases in adults with normal kidney function: The China health and retirement longitudinal study

Research have shown that sleep is associated with renal function. However, the potential effects of sleep duration or quality on kidney function in middle-aged and older Chinese adults with normal kidney function has rarely been studied. Our study aimed to investigate the association of sleep and kidney function in middle-aged and older Chinese adults. Four thousand and eighty six participants with an eGFR ≥60 ml/min/1.73 m² at baseline were enrolled between 2011 and 2015 from the China Health and Retirement Longitudinal Study. Survey questionnaire data were collected from conducted interviews in the 2011. The eGFR was estimated from serum creatinine and/or cystatin C using the Chronic Kidney Disease Epidemiology Collaboration equations (CKD-EPI). The primary outcome was defined as rapid kidney function decline. Secondary outcome was defined as rapid kidney function decline with clinical eGFR of <60 ml/min/1.73 m² at the exit visit. The associations between sleep duration, sleep quality and renal function decline or chronic kidney disease (CKD) were assessed based with logistic regression model. Our results showed that 244 (6.0%) participants developed rapid decline in kidney function, while 102 (2.5%) developed CKD. In addition, participants who had 3-7 days of poor sleep quality per week had higher risks of CKD development (OR 1.86, 95% CI 1.24-2.80). However, compared with those who had 6-8 h of night-time sleep, no significantly higher risks of rapid decline in kidney function was found among those who had <6 h or >8 h of night time sleep after adjustments for demographic, clinical, or psychosocial covariates. Furthermore, daytime nap did not present significant risk in both rapid eGFR decline or CKD development. In conclusion, sleep quality was significantly associated with the development of CKD in middle-aged and older Chinese adults with normal kidney function.

Intravitreal Vascular Endothelial Growth Factor Inhibitor Use and Renal Function Decline in Patients with Diabetic Retinopathy

Adverse renal effects of systemic vascular endothelial growth factor (VEGF) inhibitor treatment are well documented. We aimed to identify associations between intravitreal VEGF inhibitor use and renal function decline in patients with diabetic retinopathy. We included 625 patients with diabetic retinopathy for regular renal function follow-ups and grouped them according to intravitreal therapy (67 with and 558 without treatment). We used a generalized estimating equation model to identify renal function decline risk factors. Increased age (p = 0.02), insulin use (p = 0.01), hypertension (p < 0.01), and ischemic heart disease (p < 0.01) were associated with significantly decreased estimated glomerular filtration rates (eGFRs) in patients with diabetic retinopathy after 1-year follow-up. Compared to the control group, patients who received intravitreal VEGF inhibitor injections showed a declining eGFR trend in the repeated measurement model without statistical significance (p = 0.06). In subgroup analysis, patients with initial eGFR ≤ 30 mL/min/1.73 m² who received intravitreal VEGF inhibitors had significantly decreased renal function (p < 0.01) compared to those without treatment. Intravitreal VEGF inhibitor injection was associated with renal function deterioration among patients with diabetic retinopathy and advanced chronic kidney disease. Strategies to monitor renal function after treatment should be considered in these high-risk populations.

Sex Differences in Age-Related Loss of Kidney Function

BACKGROUND

CKD is more prevalent in women, but more men receive kidney replacement therapy for kidney failure. This apparent contradiction is not well understood.

METHODS

We investigated sex differences in the loss of kidney function and whether any sex disparities could be explained by comorbidity or CKD risk factors. In the Renal Iohexol Clearance Survey (RENIS) in northern Europe, we recruited 1837 persons (53% women, aged 50-62 years) representative of the general population and without self-reported diabetes, CKD, or cardiovascular disease. Participants' GFR was measured by plasma iohexol clearance in 2007-2009 (n=1627), 2013-2015 (n=1324), and 2018-2020 (n=1384). At each study visit, healthy persons were defined as having no major chronic diseases or risk factors for CKD. We used generalized additive mixed models to assess age- and sex-specific GFR decline rates.

RESULTS

Women had a lower GFR than men at baseline (mean [SD], 90.0 [14.0] versus 98.0 [13.7] ml/min per 1.73 m2; P<0.001). The mean GFR change rate was -0.96 (95% confidence interval [CI], -0.88 to -1.04) ml/min per 1.73 m2 per year in women and -1.20 (95% confidence interval [CI], -1.12 to -1.28) in men. Although the relationship between age and GFR was very close to linear in women, it was curvilinear in men, with steeper GFR slopes at older ages (nonlinear effect; P<0.001). Healthy persons had a slower GFR decline, but health status did not explain the sex difference in the GFR decline.

CONCLUSION

Among middle-aged and elderly individuals in the general population, decline in the mean GFR in women was slower than in men, independent of health status.

Various Obesity Indices and Arterial Function Evaluated with CAVI - Is Waist Circumference Adequate to Define Metabolic Syndrome?

Obesity has been known to relate to various diseases and metabolic disorders. Since the implication of body shape has been mentioned, obesity can be divided into visceral obesity and subcutaneous obesity. The former is considered the upstream pathophysiology of metabolic syndrome (MetS), and has been emphasized worldwide for the prevention of cardiovascular diseases in the last quarter century. However, some prospective studies have shown that cardiovascular mortality and morbidity are not necessarily higher in patients with MetS compared to those without. Recently, cardio-ankle vascular index (CAVI) has been established as an indicator of arteriosclerosis. This parameter is independent of blood pressure at the measuring time, and reflects systemic arterial stiffness from the aortic origin to the ankle. However, since CAVI is not necessarily high in MetS patients, attempts have been made to clarify this unexpected phenomenon. In several studies, CAVI was found to correlate negatively with body mass index (BMI), and also with waist circumference (WC) which is a widely used representative visceral obesity index. On the other hand, a body shape index (ABSI) is also a visceral obesity index designed to be minimally associated with BMI, and is calculated by dividing WC by an allometric regression of weight and height. Replacing high WC with high ABSI in MetS diagnosis promoted the identification of MetS patients with increased CAVI in cross-sectional studies on Japanese and Korean populations. Additionally, the incidence of MetS diagnosed using high ABSI was associated with significant increase in CAVI after 1 year of observation. Enhanced predictive ability for renal function decline by replacing WC with ABSI in MetS diagnosis was also observed in a longitudinal study in Japanese urban residents. These findings suggest that MetS diagnosis using high ABSI instead of high WC as a visceral obesity index needs to be reconsidered. However, further research is desirable on Caucasian, whose body shape differs slightly from that of Asians.

Comparison of Predictive Ability of Arterial Stiffness Parameters Including Cardio-Ankle Vascular Index, Pulse Wave Velocity and Cardio-Ankle Vascular Index0

Cardio-ankle vascular index (CAVI) was developed to reflect the stiffness of the arterial tree from the aortic origin to the ankle. This arterial stiffness parameter is useful for assessing the severity of cardiovascular disease (CVD) and its risk. However, compared to pulse wave velocity (PWV), the conventional gold standard of arterial stiffness parameter, there has been a concern regarding CAVI that there are fewer longitudinal studies for CVD. Furthermore, the accuracy of CAVI for atherosclerotic diseases compared to other parameters has not been well validated. This review article aims to summarize recent findings to clarify the predictive ability of CAVI in longitudinal studies. First, several large longitudinal studies have found that not only baseline CAVI but also CAVI changes during the observation period predict cardiovascular events. Second, CAVI may have superior discriminatory power for all-cause mortality and major adverse cardiovascular endpoints compared to PWV. Furthermore, one large longitudinal study found CAVI to be a stronger predictor for renal function decline compared to PWV as well as CAVI₀, a variant of CAVI that mathematically excludes BP dependence. Additionally, CAVI shows the properties that allow the elucidation of specific hemodynamics in aortic valve disease or hypovolemia. In conclusion, CAVI may be a modifiable arterial stiffness parameter not only for predicting and preventing atherosclerotic diseases but also for elucidating specific hemodynamic pathophysiology.

Inverse Association Between Baseline Plasma Selenium Concentrations and Risks of Renal Function Decline in Hypertensive Adults

BACKGROUND

The kidney has the highest level of selenium (Se) in the body, but the role of plasma Se in chronic kidney disease is uncertain.

OBJECTIVE

We aimed to investigate the longitudinal association between baseline plasma Se and renal function decline in adults with hypertension and to explore possible effect modifiers.

METHODS

This was a post hoc analysis of 935 men and women with hypertension aged 40 to 75 years from a folic-acid intervention trial (the China Stroke Primary Prevention Trial) in China. The baseline plasma Se was analyzed both as a continuous variable and as tertiles. The primary outcome was a rapid decline in renal function, defined as a mean decline in the estimated glomerular filtration rate of ≥ 5 mL/(min × 1.73 m2) per year.

RESULTS

The median follow-up duration from baseline to outcome was 4.4 years. After multivariate adjustment, there was an inverse association between plasma Se and a rapid decline in renal function (per 10-unit increment; OR: 0.85; 95% CI: 0.73, 0.99). When the baseline plasma Se was assessed as tertiles, compared to the lowest tertile (<74.5 μg/L), a lower trend of the primary outcome was found in the second tertile (74.5 to < 89.4 μg/L; OR: 0.60; 95% CI: 0.34, 1.07) and the highest tertile (89.4 to <150 μg/L; OR: 0.42; 95% CI: 0.22, 0.80; Ptrend = 0.006). Furthermore, the Se-renal association was more pronounced among participants with folic acid treatment or with a higher baseline folate concentration (both Pinteraction values < 0.05).

CONCLUSIONS

In this sample of Chinese adults with hypertension, baseline plasma Se concentrations were inversely associated with the risk of renal function decline. The China Stroke Primary Prevention Trial was registered at clinicaltrials.gov as NCT00794885.

Age and the Course of GFR in Persons Aged 70 and Above

BACKGROUND AND OBJECTIVES

In older adults, data on the age-related course of GFR are scarce, which might lead to misjudgment of the clinical relevance of reduced GFR in old age.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

To describe the course of eGFR in older adults and derive reference values in population-based individuals, we used the longitudinal design of the Berlin Initiative Study (BIS) with a repeated estimation of GFR over a median of 6.1 years of follow-up. In 2069 community-dwelling older individuals (mean inclusion age 80 years, range 70-99), GFR was estimated biennially with the BIS-2 equation, including standardized creatinine and cystatin C levels, sex, and age. We described the crude and adjusted course using a mixed-effects model and analyzed the influence of death on the GFR course applying joint models. GFR slopes were compared using GFR equations on the basis of creatinine and/or cystatin C.

RESULTS

We observed a decreasing, thus nonlinear, eGFR decline with increasing age in a population of old adults. The estimated 1-year slope for ages 75 and 90 diminished for men from -1.67 to -0.99 and for women from -1.52 to -0.97. The modeled mean eGFR for men aged ≥79 and women ≥78 was below 60 ml/min per 1.73 m². Multivariable adjustment attenuated slopes only minimally. Taking death into account by applying joint models did not alter the nonlinear eGFR decline. Using eGFR equations on the basis of creatinine only showed linear slope patterns in contrast to nonlinear patterns for equations including cystatin C.

CONCLUSIONS

The eGFR decline depended on sex and age and changed only marginally after multivariable adjustment but decelerated with increasing age. Equations including cystatin C demonstrated a nonlinear slope challenging the previously assumed linearity of the decline of eGFR in old age.

Metabolic Syndrome and Obesity-Related Indices Are Associated with Rapid Renal Function Decline in a Large Taiwanese Population Follow-Up Study

A rapid decline in renal function can cause many complications, and therefore it is important to detect associated risk factors. Few studies have evaluated the associations among obesity-related indices and metabolic syndrome (MetS) with renal function decline. This longitudinal study aimed to explore these relationships in a large cohort of Taiwanese participants. The studied obesity-related indices were waist-to-height ratio (WHtR), A body shape index (ABSI), visceral adiposity index (VAI), lipid accumulation product (LAP), waist-to-hip ratio (WHR), body roundness index (BRI), conicity index (CI), body mass index (BMI), body adiposity index (BAI) and abdominal volume index (AVI). We included 122,068 participants in the baseline study, of whom 27,033 were followed for a median of four years. The baseline prevalence of MetS was 17.7%. Multivariable analysis showed that the participants with MetS and high VAI, WHtR, WHR, LAP, CI, BRI, BMI, BAI, AVI, and ABSI values were significantly associated with a high baseline estimated glomerular filtration rate (eGFR) (all p < 0.001). In addition, the participants with MetS (p < 0.001), high WHtR (p = 0.007), low LAP (p < 0.001), high BRI (p = 0.002), high CI (p = 0.002), high AVI (p = 0.001), high VAI (p = 0.017), and high ABSI (p = 0.013) were significantly associated with a low △eGFR, indicating a rapid decline in renal function. These results showed associations between MetS and high values of obesity-related indices except LAP with high baseline eGFR and rapid decline in kidney function. These findings suggest that screening for MetS and obesity may help to slow the decline in renal function in high-risk populations.

Predictive ability of arterial stiffness parameters for renal function decline: a retrospective cohort study comparing cardio-ankle vascular index, pulse wave velocity and cardio-ankle vascular index 0

OBJECTIVE

The relative usefulness of arterial stiffness parameters on renal function remains controversial. This study aimed to compare the predictive ability of three arterial stiffness parameters at baseline; cardio-ankle vascular index (CAVI), heart-ankle pulse wave velocity (haPWV) and CAVI 0 , a variant of CAVI that theoretically excludes dependence on blood pressure, for renal function decline in Japanese general population.

METHODS

A total of 27 864 Japanese urban residents without renal impairment at baseline who participated in two to eight consecutive (mean 3.5 ± 1.7 times) annual health examinations were studied.

RESULTS

During the study period, 6.6% of participants developed renal function decline (estimated glomerular filtration rate <60 ml/min per 1.73 m 2 ), all of whom had relatively high values in all arterial stiffness parameters. In receiver-operating characteristic curve analysis, the discriminatory power for renal function decline showed a decreasing trend of CAVI to haPWV to CAVI 0 (C-statistic: 0.740 vs. 0.734 vs. 0.726). The cut-offs were CAVI 8.0, haPWV 7.23 and CAVI 0 11.6. In Cox-proportional hazards analysis for increase of each parameter above cut-off or by 1 standard deviation (SD) adjusted for two models of confounders, only CAVI always contributed significantly to renal function decline. Restricted cubic spline regression analysis suggested that CAVI most accurately reflected the risk of renal function decline.

CONCLUSION

Increase in arterial stiffness parameters, especially CAVI, may represent a major modifiable risk factor for renal function decline in the general population. Further research is needed to examine whether CAVI-lowering interventions contribute to the prevention of chronic kidney disease.

Longitudinal TNFR1 and TNFR2 and Kidney Outcomes: Results from AASK and VA NEPHRON-D

BACKGROUND

Higher baseline levels of soluble TNF receptors (TNFR1 and TNFR2) have been associated with progressive CKD. Whether longitudinal changes in these biomarkers of inflammation are also associated with worse kidney outcomes has been less studied.

METHODS

We evaluated associations of longitudinal changes in TNFR1 and TNFR2 with ESKD in the African American Study of Kidney Disease and Hypertension (AASK; 38% female; 0% diabetes) and kidney function decline (first occurrence of ≥30 ml/min per 1.73 m2 or ≥50% eGFR decline if randomization eGFR ≥60 or <60 ml/min per 1.73 m2, respectively; ESKD) in the Veterans Affairs Nephropathy in Diabetes trial (VA NEPHRON-D; 99% male; 100% diabetes) using Cox models. Biomarkers were measured from samples collected at 0-, 12-, and 24-month visits for AASK (serum) and 0- and 12-month visits for VA NEPHRON-D (plasma). Biomarker slopes (AASK) were estimated using linear mixed-effects models. Covariates included sociodemographic/clinical factors, baseline biomarker level, and kidney function.

RESULTS

There were 129 ESKD events over a median of 7.0 years in AASK (n=418) and 118 kidney function decline events over a median of 1.5 years in VA NEPHRON-D (n=754). In AASK, each 1 SD increase in TNFR1 and TNFR2 slope was associated with 2.98- and 1.87-fold higher risks of ESKD, respectively. In VA NEPHRON-D, each 1 SD increase in TNFR1 and TNFR2 was associated with 3.20- and 1.43-fold higher risks of kidney function decline, respectively.

CONCLUSIONS

Among individuals with and without diabetes, longitudinal increases in TNFR1 and TNFR2 were each associated with progressive CKD, independent of initial biomarker level and kidney function.

APOL1 Kidney Risk Variants and Proteomics

BACKGROUND AND OBJECTIVES

The APOL1 risk variants (G1 and G2) are associated with kidney disease among Black adults, but the clinical presentation is heterogeneous. In mouse models and cell systems, increased gene expression of G1 and G2 confers cytotoxicity. How APOL1 risk variants relate to the circulating proteome warrants further investigation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Among 461 African American Study of Kidney Disease and Hypertension (AASK) participants (mean age: 54 years; 41% women; mean GFR: 46 ml/min per 1.73 m2), we evaluated associations of APOL1 risk variants with 6790 serum proteins (measured via SOMAscan) using linear regression models. Covariates included age, sex, percentage of European ancestry, and protein principal components 1-5. Associated proteins were then evaluated as mediators of APOL1-associated risk for kidney failure. Findings were replicated among 875 Atherosclerosis Risk in Communities (ARIC) study Black participants (mean age: 75 years; 66% women; mean eGFR: 67 ml/min per 1.73 m2).

RESULTS

In the AASK study, having two (versus zero or one) APOL1 risk alleles was associated with lower serum levels of APOL1 (P=3.11E-13; P=3.12E-06 [two aptamers]), APOL2 (P=1.45E-10), CLSTN2 (P=2.66E-06), MMP-2 (P=2.96E-06), SPOCK2 (P=2.57E-05), and TIMP-2 (P=2.98E-05) proteins. In the ARIC study, APOL1 risk alleles were associated with APOL1 (P=1.28E-11); MMP-2 (P=0.004) and TIMP-2 (P=0.007) were associated only in an additive model, and APOL2 was not available. APOL1 high-risk status was associated with a 1.6-fold greater risk of kidney failure in the AASK study; none of the identified proteins mediated this association. APOL1 protein levels were not associated with kidney failure in either cohort.

CONCLUSIONS

APOL1 risk variants were strongly associated with lower circulating levels of APOL1 and other proteins, but none mediated the APOL1-associated risk for kidney failure. APOL1 protein level was also not associated with kidney failure.

Comparing the renal outcomes in patients with atrial fibrillation receiving different oral anticoagulants

BACKGROUND

We aimed to compare renal function changes in patients with atrial fibrillation (AF) prescribed different oral anticoagulants (OACs).

RESEARCH DESIGN AND METHODS

We performed a retrospective analysis of Australian national primary care data. A total of 12,562 patients with AF and initiated OAC between 1 Jan 2013 and 31 Dec 2017 were included. Inverse probability of treatment weighting was used for balancing baseline characteristics and the risks of decline in estimated glomerular filtration rate (eGFR) in patients prescribed each OAC were compared using Cox proportional hazards regression model.

RESULTS

Compared with warfarin, prescribing of direct-acting oral anticoagulants (DOACs) was associated with a lower risk of renal function decline per 1000 person-years: hazard ratio (HR) 0.75, 95% confidence interval (CI) 0.68-0.81, p<0.001 for ≥30% decline in eGFR; HR 0.28, 95% CI 0.20-0.41, p<0.001 for eGFR decline to ≤30 mL/min/1.73m²; and HR 0.45, 95% CI 0.35-0.58, p<0.001 for serum creatinine doubling. Compared with dabigatran, rivaroxaban use had a significantly lowered risk of decline in eGFR to ≤30 mL/min/1.73m² (HR 0.29, 95% CI 0.13-0.66, p=0.003) and risk of doubling of serum creatinine (HR 0.62, 95% CI 0.40-0.95, p=0.030).

CONCLUSIONS

The risk of renal function decline appeared to be lower in patients prescribed DOACs versus warfarin.

Sepsis and the Risks of Long-Term Renal Adverse Outcomes in Patients With Chronic Kidney Disease

Background

Sepsis is known to cause renal function fluctuations during hospitalization, but whether these patients discharged from sepsis were still at greater risks of long-term renal adverse outcomes remains unknown.

Methods

From 2011 to 2018, we included 1,12,628 patients with chronic kidney disease (CKD) aged ≥ 20 years. The patients with CKD were further divided into 11,661 sepsis group and 1,00,967 non-sepsis group. The following outcome of interest was included: all-cause mortality, readmission for acute kidney injury, estimated glomerular filtration rate decline ≥50% or doubling of serum creatinine, and end-stage renal disease.

Results

After propensity score matching, the sepsis group was at higher risks of all-cause mortality [hazard ratio (HR) 1.39, 95% CI, 1.31–1.47], readmission for acute kidney injury (HR 1.67, 95% CI 1.58–1.76), eGFR decline ≥ 50% or doubling of serum creatinine (HR 3.34, 95% CI 2.78–4.01), and end-stage renal disease (HR 1.43, 95% CI 1.34–1.53) than non-sepsis group.

Conclusions

Our study found that patients with CKD discharged from hospitalization for sepsis have higher risks of subsequent renal adverse events.

Risk factors and prevention for postoperative delirium after orthopedic surgery

BACKGROUND

Postoperative delirium significantly delays the recovery of patients. This study sought to explore the risk factors and to prevent postoperative delirium after orthopedic surgery.

MATERIALS AND METHODS

In the part of retrospective study, 456 cases over 70-year-old that underwent one of three types of orthopedic surgery were included and were defined as the retrospective group. The risk factors of postoperative delirium were analyzed by logistic regression. In the part of prospective study, 86 cases of the same age and the same surgery were included and were defined as the prospective group. Positive interventions were used by shortening the fasting time and increasing the perioperative rehydration. The differences of postoperative delirium incidence between the retrospective group and the prospective group were analyzed.

RESULTS

Compared with patients with normal postoperative electrolytes, postoperative creatinine <68.20 μmol/L, and fluid infusion during fasting >119.66 mL/h, postoperative electrolyte disorders (odds ratio [OR]: 2.864; 95% confidence interval [CI]: 1.374, 5.970), postoperative creatinine ≥68.20 μmol/L (OR: 2.660; 95% CI: 1.328, 5.328), and fluid infusion during fasting ≤119.66 mL/h (OR: 2.372; 95% CI: 1.197, 4.704) were the risk factors for postoperative delirium. After positive intervention, the postoperative delirium incidence of the prospective group was 5.8% (5/86), and it was lower than 18.4% (84/456) of the retrospective group (P < 0.05).

CONCLUSIONS

Elevated postoperative creatinine, postoperative electrolyte disorders, and lower fluid infusion during fasting were three risk factors for postoperative delirium. By shortening the fasting time and increasing the perioperative rehydration, the incidence of postoperative delirium could be reduced.

Urinary excretion of epidermal growth factor and rapid loss of kidney function

BACKGROUND

Lower urinary excretion of the kidney tubule-specific biomarker epidermal growth factor (uEGF) is associated with increased risk of renal function [glomerular filtration rate (GFR)] loss in diabetes and in patients with established chronic kidney disease (CKD). We investigated whether uEGF is associated with rapid GFR decline or incident CKD in the general population.

METHODS

Subjects without CKD or diabetes were recruited from the general population in Tromso, Norway [Renal Iohexol Clearance Survey (RENIS); N = 1249] and Groningen, the Netherlands [Prevention of REnal and Vascular END-stage disease (PREVEND); N = 4534], with a median follow-up of 5.6 and 7.4 years, respectively. GFR was measured by iohexol clearance in the RENIS and estimated using the CKD Epidemiology Collaboration creatinine-cystatin C equation in the PREVEND study. Rapid GFR decline was defined as an annual GFR loss >3.0 mL/min/1.73 m2 and in sensitivity analyses as subjects with the 10% steepest GFR slope within each cohort.

RESULTS

Lower baseline uEGF excretion was associated with rapid GFR loss in both cohorts {RENIS, odds ratio [OR] per 1 μg/mmol lower uEGF 1.42 [95% confidence interval (CI) 1.06-1.91], P = 0.02; PREVEND, OR 1.29 [95% CI 1.10-1.53], P < 0.01}, adjusted for baseline GFR, albumin:creatinine ratio and conventional CKD risk factors. Similar results were obtained using the outcome of the 10% steepest GFR slope in each cohort. Lower uEGF levels were associated with incident CKD in the combined analysis of both cohorts.

CONCLUSIONS

Lower uEGF levels are associated with increased risk of rapid GFR loss and incident CKD in the general population. This finding, together with previous findings in CKD and high-risk populations, supports that uEGF may serve as a broadly applicable biomarker representing the tubular component of the current glomerulus-centric clinical risk assessment system.

Ertugliflozin and Slope of Chronic eGFR: Prespecified Analyses from the Randomized VERTIS CV Trial

BACKGROUND AND OBJECTIVES

A reduction in the rate of eGFR decline, with preservation of ≥0.75 ml/min per 1.73 m² per year, has been proposed as a surrogate for kidney disease progression. We report results from prespecified analyses assessing effects of ertugliflozin versus placebo on eGFR slope from the eValuation of ERTugliflozin effIcacy and Safety CardioVascular outcomes (VERTIS CV) trial (NCT01986881).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Patients with type 2 diabetes mellitus and established atherosclerotic cardiovascular disease were randomized to placebo, ertugliflozin 5 mg, and ertugliflozin 15 mg (1:1:1). The analyses compared the effect of ertugliflozin (pooled doses, n=5499) versus placebo (n=2747) on eGFR slope per week and per year by random coefficient models. Study periods (weeks 0-6 and weeks 6-52) and total and chronic slopes (week 0 or week 6 to weeks 104, 156, 208, and 260) were modeled separately and by baseline kidney status.

RESULTS

In the overall population, for weeks 0-6, the least squares mean eGFR slopes (ml/min per 1.73 m² per week [95% confidence interval (95% CI)]) were -0.07 (-0.16 to 0.03) and -0.54 (-0.61 to -0.48) for the placebo and ertugliflozin groups, respectively; the difference was -0.47 (-0.59 to -0.36). During weeks 6-52, least squares mean eGFR slopes (ml/min per 1.73 m² per year [95% CI]) were -0.12 (-0.70 to 0.46) and 1.62 (1.21 to 2.02) for the placebo and ertugliflozin groups, respectively; the difference was 1.74 (1.03 to 2.45). For weeks 6-156, least squares mean eGFR slopes (ml/min per 1.73 m² per year [95% CI]) were -1.51 (-1.70 to -1.32) and -0.32 (-0.45 to -0.19) for the placebo and ertugliflozin groups, respectively; the difference was 1.19 (0.95 to 1.42). During weeks 0-156, the placebo-adjusted difference in least squares mean slope was 1.06 (0.85 to 1.27). These findings were consistent by baseline kidney status.

CONCLUSIONS

Ertugliflozin has a favorable placebo-adjusted eGFR slope >0.75 ml/min per 1.73 m² per year, documenting the kidney function preservation underlying the clinical benefits of ertugliflozin on kidney disease progression in patients with type 2 diabetes mellitus and atherosclerotic cardiovascular disease.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

US National Library of Medicine, ClinicalTrials.gov NCT01986881. Date of trial registration: November 13, 2013.

Changes in GFR and Albuminuria in Routine Clinical Practice and the Risk of Kidney Disease Progression

RATIONALE & OBJECTIVE

Changes in urinary albumin-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) have been used separately as alternative kidney disease outcomes in randomized trials. We tested the hypothesis that combined changes in UACR and eGFR predict advanced kidney disease better than either alone.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

91,319 primary care patients assembled from the Clinical Practice Research Datalink in the United Kingdom between 2000 and 2015.

EXPOSURES

Changes in UACR and eGFR (categorized as ≥30% increase, stable, or ≥30% decrease), alone and in combination, over a 3-year period.

OUTCOMES

The primary outcome was advanced CKD (sustained eGFR <30 mL/min/1.73 m2); secondary outcomes included kidney failure, cardiovascular disease, and all-cause mortality.

ANALYTICAL APPROACH

Multivariable Cox regression with bias from missing values assessed using multiple imputation; discrimination statistics compared across exposure groups.

RESULTS

91,319 individuals were studied, with a mean eGFR of 72.6 mL/min/1.73 m2 and median UACR of 9.7 mg/g; 70,957 (77.7%) had diabetes. During a median follow-up of 2.9 years, 2,541 people progressed to advanced CKD. Compared with stable values, hazard ratios for a ≥30% increase in UACR and ≥30% decrease in eGFR were 1.78 (95% CI, 1.59-1.98) and 7.53 (95% CI, 6.70-8.45), respectively, for the outcome of advanced CKD. Compared with stable values of both, the hazard ratio for the combination of an increase in UACR and a decrease in eGFR was 15.15 (95% CI, 12.43-18.46) for the outcome of advanced CKD. The combination of changes in UACR and eGFR predicted kidney outcomes better than either alone.

LIMITATIONS

Selection bias, relatively small proportion of individuals without diabetes, and very few kidney failure events.

CONCLUSIONS

In a large-scale general population, the combination of an increase in UACR and a decrease in eGFR was strongly associated with the risk of advanced CKD. Further assessment of combined changes in UACR and eGFR as an alternative outcome for kidney failure in trials of CKD progression is warranted.

Renal function decline in older men and women with advanced chronic kidney disease-results from the EQUAL study

INTRODUCTION

Understanding the mechanisms underlying the differences in renal decline between men and women may improve sex-specific clinical monitoring and management. To this end, we aimed to compare the slope of renal function decline in older men and women in chronic kidney disease (CKD) Stages 4 and 5, taking into account informative censoring related to the sex-specific risks of mortality and dialysis initiation.

METHODS

The European QUALity Study on treatment in advanced CKD (EQUAL) study is an observational prospective cohort study in Stages 4 and 5 CKD patients ≥65 years not on dialysis. Data on clinical and demographic patient characteristics were collected between April 2012 and December 2018. Estimated glomerular filtration rate (eGFR) was calculated using the CKD Epidemiology Collaboration equation. eGFR trajectory by sex was modelled using linear mixed models, and joint models were applied to deal with informative censoring.

RESULTS

We included 7801 eGFR measurements in 1682 patients over a total of 2911 years of follow-up. Renal function declined by 14.0% [95% confidence interval (CI) 12.9-15.1%] on average each year. Renal function declined faster in men (16.2%/year, 95% CI 15.9-17.1%) compared with women (9.6%/year, 95% CI 6.3-12.1%), which remained largely unchanged after accounting for various mediators and for informative censoring due to mortality and dialysis initiation. Diabetes was identified as an important determinant of renal decline specifically in women.

CONCLUSION

In conclusion, renal function declines faster in men compared with women, which remained similar after adjustment for mediators and despite a higher risk of informative censoring in men. We demonstrate a disproportional negative impact of diabetes specifically in women.

Metabolic Acidosis Is an Independent Risk Factor of Renal Progression in Korean Chronic Kidney Disease Patients: The KNOW-CKD Study Results

Background: We aimed to evaluate serum bicarbonate as a risk factor for renal progression, cardiovascular events, and mortality in Korean CKD patients.

Methods: We analyzed 1,808 participants from a Korean CKD cohort whose serum bicarbonate levels were measured at enrollment. Serum bicarbonate levels were categorized as low, lower normal, higher normal, and high (total carbon dioxide <22, 22–26, 26.1–29.9, and ≥30 mmol/L, respectively) groups. Metabolic acidosis was defined as a serum bicarbonate level <22 mmol/L. The primary outcome was renal events defined as doubling of serum creatinine, 50% reduction of eGFR from the baseline values, or development of end-stage kidney disease. The secondary outcome consisted of cardiovascular events and death. In addition, patients whose eGFR values were measured more than three times during the follow-up period were analyzed for eGFR decline. The rapid decline in eGFR was defined as lower than the median value of the eGFR slope.

Results: The mean serum bicarbonate level was 25.7 ± 3.7 mmol/L and 240 (13.2%) patients had metabolic acidosis. During the follow-up period of 55.2 ± 24.1 months, 545 (30.9%) patients developed renal events and 187 (10.6%) patients developed a composite of cardiovascular events and death. After adjustment, the low serum bicarbonate group experienced 1.27 times more renal events than the lower normal bicarbonate group [hazard ratio (HR): 1.27; 95% CI: 1.01–1.60, P = 0.043]. There was no significant association between the bicarbonate groups and the composite outcome of cardiovascular events and death. The low bicarbonate group showed a significantly rapid decline in eGFR [odds ratio (OR): 2.12; 95% CI: 1.39–3.22, P < 0.001] compared to the lower normal bicarbonate group.

Conclusions: Metabolic acidosis was significantly associated with increased renal events and a rapid decline in renal function in Korean predialysis CKD patients.

The Association of the Oxford Classification Score with Longitudinal Estimated Glomerular Filtration Rate Decline in Patients with Immunoglobulin A Nephropathy: A Mixed-Method Study

Introduction

The Oxford Classification score, which predicts renal outcomes for immunoglobulin A nephropathy (IgAN), is widely used in clinical practice. Nevertheless, the relationship between these markers and longitudinal changes in renal function are poorly understood.

Methods

This was a population-based retrospective cohort study of 280 adults with biopsy-proven primary IgAN from 2011 to 2018. We used generalized additive mixed models to control for traditional kidney disease risk factors to analyze the associations between Oxford Classification MEST-C scores (mesangial hypercellularity, M; endocapillary hypercellularity, E; segmental glomerulosclerosis, S; tubular atrophy/interstitial fibrosis, T; crescents, C) and longitudinal changes in the estimated glomerular filtration rate (eGFR) after renal biopsy.

Results

The median eGFR was 78.2 mL/min/1.73 m² at baseline, and then it decreased on average by 1.3 mL/min/1.73 m² per year in the entire cohort. In adjusted models, compared with patients without relative lesions, the presence of T > 50% (T2) (−5.7; 95% confidence interval [CI], −9.5 to −2.0 mL/min/1.73m² per year) was associated with the fastest eGFR decline. S present (S1) (−2.9; 95% CI, −4.6 to −1.1 mL/min/1.73m² per year) and C > 25% glomeruli (C2) (−3.4; 95% CI, −6.4 to −0.5 mL/min/1.73m² per year) also demonstrated steeper eGFR declines. However, we found no association between M > 0.5 (M1), E present (E1), T 26%–50% (T1), and C present ≥ 1 glomerulus (C1), and progressive eGFR decline (p > 0.05).

Conclusion

The Oxford Classification scores, S1, T2, and C2, were independently associated with the longitudinal decreases in renal function in patients with IgAN. These findings suggested therapies targeted at improving early damage to these lesions might be essential to delay renal progression.

Multiplex Serum Biomarker Assays Improve Prediction of Renal and Mortality Outcomes in Chronic Kidney Disease

BACKGROUND

We investigated the predictive value of 11 serum biomarkers for renal and mortality end points in people with CKD.

METHODS

Adults with CKD (n=139) were enrolled from outpatient clinics between February 2014 and November 2016. Biomarker quantification was performed using two multiplex arrays on a clinical-grade analyzer. Relationships between biomarkers and renal and mortality end points were investigated by random forests and Cox proportional hazards regression.

RESULTS

The cohort was 56% male. The mean age was 63 years and median (IQR) CKD-EPI eGFR was 33 (24-51) ml/min per BSA. A total of 56 (40%) people developed a composite end point defined as ≥40% decline in eGFR, doubling of serum creatinine, RRT, or death over median (IQR) follow-up of 5.4 (4.7-5.7) years. Prediction of the composite end point was better with random forests trained on serum biomarkers compared with clinical variables (area under the curve of 0.81 versus 0.78). The predictive performance of biomarkers was further enhanced when considered alongside clinical variables (area under the curve of 0.83 versus 0.81 for biomarkers alone). Patients (n=27, 19%) with high soluble TNF receptor-1 (≥3 ng/ml) and neutrophil gelatinase-associated lipocalin (≥156 ng/ml), coupled with low complement 3a des-arginine (<2368 ng/ml), almost universally (96%) developed the composite renal and mortality end point. C-reactive protein (adjusted hazard ratio, 1.4; 95% CI, 1.1 to 1.8), neutrophil gelatinase-associated lipocalin (adjusted hazard ratio, 2.8; 95% CI, 1.3 to 6.1) and complement 3a desarginine (adjusted hazard ratio, 0.6; 95% CI, 0.4 to 0.96) independently predicted time to the composite end point.

CONCLUSIONS

Outpatients with the triad of high soluble TNF receptor-1 and neutrophil gelatinase-associated lipocalin coupled with low complement 3a des-arginine had high adverse event rates over 5-year follow-up. Incorporation of serum biomarkers alongside clinical variables improved prediction of CKD progression and mortality. Our findings require confirmation in larger, more diverse patient cohorts.

Risks of AKI and Major Adverse Clinical Outcomes in Patients with Severe Acute Respiratory Syndrome or Coronavirus Disease 2019

BACKGROUND

Severe acute respiratory syndrome (SARS) and coronavirus disease 2019 (COVID-19) are closely related. The effect of AKI on the clinical outcomes of these two conditions is unclear.

METHODS

This retrospective, territory-wide cohort study used an electronic public healthcare database in Hong Kong to identify patients with SARS or COVID-19 by diagnosis codes, virologic results, or both. The primary endpoint was a composite of intensive care unit admission, use of invasive mechanical ventilation, and/or death.

RESULTS

We identified 1670 patients with SARS and 1040 patients with COVID-19 (median ages, 41 versus 35 years, respectively). Among patients with SARS, 26% met the primary endpoint versus 5.3% of those with COVID-19. Diabetes mellitus, abnormal liver function, and AKI were factors significantly associated with the primary endpoint among patients with either SARS or COVID-19. Among patients with SARS, 7.9%, 2.1%, and 3.7% developed stage 1, stage 2, and stage 3 AKI, respectively; among those with COVID-19, 6.6%, 0.4%, and 1.1% developed stage 1, stage 2, and stage 3 AKI, respectively. In both groups, factors significantly associated with AKI included diabetes mellitus and hypertension. Among patients with AKI, those with COVID-19 had a lower rate of major adverse clinical outcomes versus patients with SARS. Renal function recovery usually occurred within 30 days after an initial AKI event.

CONCLUSIONS

AKI rates were higher among patients with SARS than those with COVID-19. AKI was associated with major adverse clinical outcomes for both diseases. Patients with diabetes mellitus and abnormal liver function were also at risk of developing severe consequences after SARS and COVID-19 infection.

Use of the Urine-to-Plasma Urea Ratio to Predict ADPKD Progression

BACKGROUND AND OBJECTIVES

Predicting disease progression in patients with autosomal dominant polycystic kidney disease (ADPKD) poses a challenge, especially in early-stage disease when kidney function is not yet affected. Ongoing growth of cysts causes maximal urine-concentrating capacity to decrease from early on. We therefore hypothesized that the urine-to-plasma urea ratio, as a reflection of the urine-concentrating capacity, can be used as a marker to predict ADPKD progression.

DESIGN

The urine-to-plasma urea ratio was calculated by dividing concentrations of early morning fasting spot urine urea by plasma urea. First, this ratio was validated as surrogate marker in 30 patients with ADPKD who underwent a prolonged water deprivation test. Thereafter, association with kidney outcome was evaluated in 583 patients with ADPKD with a broad range of kidney function. Multivariable mixed-model regression was used to assess association with eGFR slope, and logarithmic regression to identify patients with rapidly progressive disease, using a cutoff of -3.0 ml/min per 1.73 m² per year. The urine-to-plasma urea ratio was compared with established predictors, namely, sex, age, baseline eGFR, Mayo Clinic height-adjusted total kidney volume class, and PKD gene mutation.

RESULTS

The maximal urine-concentrating capacity and urine-to-plasma urea ratio correlated strongly (R=0.90; P<0.001). Next, the urine-to-plasma urea ratio was significantly associated with rate of eGFR decline during a median follow-up of 4.0 (interquartile range, 2.6-5.0) years, both crude and after correction for established predictors (β=0.58; P=0.02). The odds ratio of rapidly progressive disease was 1.35 (95% confidence interval, 1.19 to 1.52; P<0.001) for every 10 units decrease in urine-to-plasma urea ratio, with adjustment for predictors. A combined risk score of the urine-to-plasma urea ratio, Mayo Clinic height-adjusted total kidney volume class, and PKD mutation predicted rapidly progressive disease better than each of the predictors separately.

CONCLUSIONS

The urine-to-plasma urea ratio, which is calculated from routine laboratory measurements, predicts disease progression in ADPKD in addition to other risk markers.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2021_01_27_CJN10470620_final.mp3.

Quantifying Duration of Proteinuria Remission and Association with Clinical Outcome in IgA Nephropathy

BACKGROUND

On the basis of findings of observational studies and a meta-analysis, proteinuria reduction has been proposed as a surrogate outcome in IgA nephropathy. How long a reduction in proteinuria needs to be maintained to mitigate the long-term risk of disease progression is unknown.

METHODS

In this retrospective multiethnic cohort of adult patients with IgA nephropathy, we defined proteinuria remission as a ≥25% reduction in proteinuria from the peak value after biopsy, and an absolute reduction in proteinuria to <1 g/d. The exposure of interest was the total duration of first remission, treated as a time-varying covariate using longitudinal proteinuria measurements. We used time-dependent Cox proportional hazards regression models to quantify the association between the duration of remission and the primary outcome (ESKD or a 50% reduction in eGFR).

RESULTS

During a median follow-up of 3.9 years, 274 of 1864 patients (14.7%) experienced the primary outcome. The relationship between duration of proteinuria remission and outcome was nonlinear. Each 3 months in sustained remission up to approximately 4 years was associated with an additional 9% reduction in the risk of disease progression (hazard ratio [HR], 0.91; 95% confidence interval [95% CI], 0.89 to 0.93). Thereafter, each additional 3 months in remission was associated with a smaller, nonsignificant risk reduction (HR, 0.99; 95% CI, 0.96 to 1.03). These findings were robust to multivariable adjustment and consistent across clinical and histologic subgroups.

CONCLUSIONS

Our findings support the use of proteinuria as a surrogate outcome in IgA nephropathy, but additionally demonstrate the value of quantifying the duration of proteinuria remission when estimating the risk of hard clinical endpoints.

Ultra-Processed Food Consumption is Associated with Renal Function Decline in Older Adults: A Prospective Cohort Study

Ultra-processed food (UPF) consumption has been associated with increased risk of cardiovascular risk factors and mortality. However, little is known on the UPF effect on renal function. The aim of this study is to assess prospectively the association between consumption of UPF and renal function decline. This is a prospective cohort study of 1312 community-dwelling individuals aged 60 and older recruited during 2008-2010 and followed up to December 2015. At baseline, a validated dietary history was obtained. UPF was identified according to NOVA classification. At baseline and at follow-up, serum creatinine (SCr) and estimated glomerular filtration rate (eGFR) levels were ascertained and changes were calculated. A combined end-point of renal decline was considered: SCr increase or eGFR decreased beyond that expected for age. Logistic regression with adjustment for potential confounders was performed. During follow-up, 183 cases of renal function decline occurred. The fully adjusted odds ratios (95% CI) of renal function decline across terciles of percentage of total energy intake from UPF were 1.56 (1.02-2.38) for the second tercile, and 1.74 (1.14-2.66) for the highest tercile; p-trend was 0.026. High UPF consumption is independently associated with an increase higher than 50% in the risk of renal function decline in Spanish older adults.

Risk of Renal Function Decline in Patients with Ketamine-Associated Uropathy

Ketamine-associated diseases have been increasing with the rise in ketamine abuse. Ketamine-associated uropathy is one of the most common complications. We investigated the effects of ketamine-associated uropathy on renal health and determined predictors of renal function decline in chronic ketamine abusers. This retrospective cohort study analyzed 51 patients (22 with ketamine-associated hydronephrosis and 29 with ketamine cystitis) from Kaohsiung Veterans General Hospital in Taiwan. Primary renal outcome was end-stage renal disease or estimated glomerular filtration rate decline >30% from baseline. Compared with the ketamine cystitis group, the hydronephrosis group had lower initial and final estimated glomerular filtration rates and higher alkaline phosphatase and gamma-glutamyl transferase levels (p < 0.05). Elevated cholestatic liver enzyme levels correlated with renal dysfunction in ketamine-associated uropathy. The hydronephrosis group had a higher proportion of patients reaching endpoints than the ketamine cystitis group (50% and 7%, respectively, p < 0.001). After adjusting for age, sex, and initial serum creatinine level, hydronephrosis remained an independent risk factor for renal function deterioration. Ketamine-associated hydronephrosis was a poor renal outcome and strong predictor of renal function decline in chronic ketamine abusers. Elevated cholestatic liver enzyme levels correlated with the severity of ketamine-associated uropathy. Ultrasonography screening of these high-risk groups and regular renal function follow-ups are necessary.

Arterial stiffness and kidney disease progression in the systolic blood pressure intervention trial

AIMS

Arterial stiffness increases with both advancing age and chronic kidney disease (CKD) and may contribute to kidney function decline, but evidence is inconsistent. We hypothesized that greater baseline arterial stiffness (assessed as pulse pressure (PP) and carotid-femoral pulse-wave velocity CFPWV)) was independently associated with kidney disease progression over the follow-up period (3.8 years) in the Systolic Blood Pressure Intervention Trial (SPRINT).

MATERIALS AND METHODS

8,815 SPRINT participants were included in the analysis of PP. 592 adults who participated in a SPRINT ancillary study that measured CFPWV were included in subgroup analyses. Cox proportional hazards analysis was used to examine the association between PP and time to kidney disease progression endpoints: (A) incident estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m2 in non-CKD participants at baseline; (B) 50% decline in eGFR, initiation of dialysis, or transplant in those with baseline CKD. Mixed model analyses examined the association of baseline PP/CFPWV with follow-up eGFR.

RESULTS AND CONCLUSION

Mean ± SD age was 68 ± 10 years, baseline PP was 62 ± 14 mmHg, and CFPWV was 10.8 ± 2.7 m/s. In the fully adjusted model, PP ≥ median was associated with an increased hazard of kidney disease progression endpoints (HR: 1.93 (1.43 - 2.61)). The association remained significant in individuals without (2.05 (1.47 - 2.87)) but not with baseline CKD (1.28 (0.55 - 2.65)). In fully adjusted models, higher baseline PP associated with eGFR decline (p < 0.0001 (all, CKD, non-CKD)), but baseline CFPWV did not. Among older adults at high risk for cardiovascular events, baseline PP was associated with kidney disease progression.

GFR in Healthy Aging: an Individual Participant Data Meta-Analysis of Iohexol Clearance in European Population-Based Cohorts

BACKGROUND

Population mean GFR is lower in older age, but it is unknown whether healthy aging is associated with preserved rather than lower GFR in some individuals.

METHODS

We investigated the cross-sectional association between measured GFR, age, and health in persons aged 50-97 years in the general population through a meta-analysis of iohexol clearance measurements in three large European population-based cohorts. We defined a healthy person as having no major chronic disease or risk factors for CKD and all others as unhealthy. We used a generalized additive model to study GFR distribution by age according to health status.

RESULTS

There were 935 (22%) GFR measurements in persons who were healthy and 3274 (78%) in persons who were unhealthy. The mean GFR was lower in older age by -0.72 ml/min per 1.73 m² per year (95% confidence interval [95% CI], -0.96 to -0.48) for men who were healthy versus -1.03 ml/min per 1.73 m² per year (95% CI, -1.25 to -0.80) for men who were unhealthy, and by -0.92 ml/min per 1.73 m² per year (95% CI, -1.14 to -0.70) for women who were healthy versus -1.22 ml/min per 1.73 m² per year (95% CI, -1.43 to -1.02) for women who were unhealthy. For healthy and unhealthy people of both sexes, both the 97.5th and 2.5th GFR percentiles exhibited a negative linear association with age.

CONCLUSIONS

Healthy aging is associated with a higher mean GFR compared with unhealthy aging. However, both the mean and 97.5 percentiles of the GFR distribution are lower in older persons who are healthy than in middle-aged persons who are healthy. This suggests that healthy aging is not associated with preserved GFR in old age.

Time-averaged serum uric acid and 10-year incident diabetic kidney disease: A prospective study from China

BACKGROUND

The association between serum uric acid (SUA) and the risk of diabetic kidney diseases (DKD) remains controversial. We aim to investigate the association between time-averaged SUA and long-term incident DKD among general population-based patients with diabetes.

METHODS

Altogether 1327 patients with diabetes and without kidney disease (estimated glomerular filtration rate [eGFR] ≥ 60 mL/min/1.73m² , and without proteinuria) were included. Incident DKD were defined by the occurrence of renal function decline (eGFR<60 mL/min/1.73m² ) and/or macroalbuminuria (urinary albumin-creatinine-ratio ≥ 30 mg/mM creatinine). The associations between baseline and time-averaged SUA and DKD were analyzed.

RESULTS

The mean age was 53.7 ± 8.0. During 10.2 ± 0.4 years' follow-up, 85 (6.4%) patients developed renal function decline and 101 (7.6%) patients developed macroalbuminuria. Compared to those with time-averaged SUA in the second quartile (207-240 μM/L for women, 233-272 μM/L for men), odds ratio (OR) for renal function decline was 1.92 (95% confidence interval [CI], 1.02 to 3.62; P = .04) among those with SUA in the top quartile (women≥285 μM/L; men≥324 μM/L); and OR for macroalbuminuria was 1.86 (95% CI 1.01 to 3.43; P = .05) among those with SUA in the bottom quartile (women ≤207 μM/L; men ≤233 μM/L)). No significant associations were observed between baseline SUA with incident DKD.

CONCLUSIONS

Long-term exposure to both high and low SUA level are associated with increased risk of incident DKD among patients with diabetes.

Urinary Sediment Transcriptomic and Longitudinal Data to Investigate Renal Function Decline in Type 1 Diabetes

Introduction: Using a discovery/validation approach we investigated associations between a panel of genes selected from a transcriptomic study and the estimated glomerular filtration rate (eGFR) decline across time in a cohort of type 1 diabetes (T1D) patients. Experimental: Urinary sediment transcriptomic was performed to select highly modulated genes in T1D patients with rapid eGFR decline (decliners) vs. patients with stable eGFR (non-decliners). The selected genes were validated in samples from a T1D cohort (n = 54, mean diabetes duration of 21 years, 61% women) followed longitudinally for a median of 12 years in a Diabetes Outpatient Clinic. Results: In the discovery phase, the transcriptomic study revealed 158 genes significantly different between decliners and non-decliners. Ten genes increasingly up or down-regulated according to renal function worsening were selected for validation by qRT-PCR; the genes CYP4F22, and PMP22 were confirmed as differentially expressed comparing decliners vs. non-decliners after adjustment for potential confounders. CYP4F22, LYPD3, PMP22, MAP1LC3C, HS3ST2, GPNMB, CDH6, and PKD2L1 significantly modified the slope of eGFR in T1D patients across time. Conclusions: Eight genes identified as differentially expressed in the urinary sediment of T1D patients presenting different eGFR decline rates significantly increased the accuracy of predicted renal function across time in the studied cohort. These genes may be a promising way of unveiling novel mechanisms associated with diabetic kidney disease progression.

Incidence of ESKD and Mortality among Children with Congenital Heart Disease after Cardiac Surgery

BACKGROUND AND OBJECTIVES

Survival after surgical repair for congenital heart disease has markedly improved; however, there are limited data on long-term ESKD and mortality during childhood.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted an observational, population-based cohort study of children who had their first surgery for congenital heart disease within 10 years of birth. The study was conducted in Ontario, Canada, where residents have universal access to health care services. Each child who underwent surgical repair was matched to ten children from the general population who were similar in age, sex, index date, rurality, and neighborhood income. Primary outcomes of all-cause mortality and ESKD were reported until March 2015.

RESULTS

We followed 3600 children with congenital heart disease for a median of 5.9 (interquartile range, 2.9-9.0) years after their surgical repair. Median age at first surgery was 150 (interquartile range, 40-252) days and 22% were low birth weight (<2500 g). During follow-up, 140 (4%) children who had surgery for congenital heart disease died and 52 (1%) reached ESKD. The cumulative incidence of death and ESKD at 1, 5, and 10 years was higher in children with surgical repair of congenital heart disease (death: 3%, 4%, and 5%, respectively; ESKD: 1%, 2%, and 2%, respectively) compared with the matched control population without any congenital heart disease (death: 0.06%, 0.10%, and 0.13%, respectively; ESKD: 0.00%, 0.02%, and 0.02%, respectively). The risk of ESKD and death increased with severity of congenital heart disease, with the highest risk in children with hypoplastic left heart syndrome and increased in children who had surgical repair of congenital heart disease compared with those without surgical repair.

CONCLUSIONS

The risk of mortality and ESKD is high in children who undergo surgical repair for congenital heart disease compared to the general population.

Urinary Melamine Levels and Progression of CKD

BACKGROUND AND OBJECTIVES

CKD is a global public health problem. Some cross-sectional studies have associated environmental melamine exposure with kidney diseases, but evidence is limited.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted this prospective cohort study to enroll patients with eGFR≥30 ml/min per 1.73 m² in 2006-2010. Urinary corrected melamine levels (ratio of urinary melamine to urinary creatinine) were measured by liquid chromatography/tandem mass spectrometry at enrollment. Kidney outcomes included doubling of serum creatinine levels, eGFR decline >3 ml/min per 1.73 m² per year, and 30% decline in eGFR in the first 2 years. Subjects were followed until targeted kidney outcomes, cancer, death, last contact, or the end of observation in December 2016.

RESULTS

In a total of 293 subjects, the median urinary corrected melamine level was 0.97 (interquartile range, 0.43-2.08) μg/mmol. Over a median follow-up period of 7.0 years, serum creatinine levels doubled in 80 subjects (27%). Subjects in the highest tertile of urinary melamine level 12.70 μg/mmol) had a 2.30 (95% confidence interval, 1.25 to 4.23; P<0.01) hazard risk for doubling of serum creatinine compared with those in the lowest tertile (0.02-0.58 μg/mmol). Similar significant dose-response results were found in eGFR decline >3 ml/min per 1.73 m² per year and 30% decline in eGFR in the first 2 years.

CONCLUSIONS

Urinary melamine level is significantly associated with kidney function deterioration in patients with early-stage CKD.

Renal Perfusion during Hemodialysis: Intradialytic Blood Flow Decline and Effects of Dialysate Cooling

BACKGROUND

Residual renal function (RRF) confers survival in patients with ESRD but declines after initiating hemodialysis. Previous research shows that dialysate cooling reduces hemodialysis-induced circulatory stress and protects the brain and heart from ischemic injury. Whether hemodialysis-induced circulatory stress affects renal perfusion, and if it can be ameliorated with dialysate cooling to potentially reduce RRF loss, is unknown.

METHODS

We used renal computed tomography perfusion imaging to scan 29 patients undergoing continuous dialysis under standard (36.5°C dialysate temperature) conditions; we also scanned another 15 patients under both standard and cooled (35.0°C) conditions. Imaging was performed immediately before, 3 hours into, and 15 minutes after hemodialysis sessions. We used perfusion maps to quantify renal perfusion. To provide a reference to another organ vulnerable to hemodialysis-induced ischemic injury, we also used echocardiography to assess intradialytic myocardial stunning.

RESULTS

During standard hemodialysis, renal perfusion decreased 18.4% (P<0.005) and correlated with myocardial injury (r=-0.33; P<0.05). During sessions with dialysis cooling, patients experienced a 10.6% decrease in perfusion (not significantly different from the decline with standard hemodialysis), and ten of the 15 patients showed improved or no effect on myocardial stunning.

CONCLUSIONS

This study shows an acute decrease in renal perfusion during hemodialysis, a first step toward pathophysiologic characterization of hemodialysis-mediated RRF decline. Dialysate cooling ameliorated this decline but this effect did not reach statistical significance. Further study is needed to explore the potential of dialysate cooling as a therapeutic approach to slow RRF decline.

Serum Lipids and Risk of Rapid Renal Function Decline in Treated Hypertensive Adults With Normal Renal Function

BACKGROUND

We aim to evaluate the effect of different lipids parameters, including triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), the TG to HDL-C (TG:HDL-C) ratio, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C), on the risk of rapid renal function decline and examine any possible effect modifiers in general hypertensive patients with normal renal function.

METHODS

A total of 12,549 hypertensive patients with estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73 m2 in the renal sub-study of the China Stroke Primary Prevention Trial were included in the analyses. The primary outcome was rapid renal function decline, defined as an average decline in eGFR ≥ 5 ml/min/1.73 m2 per year.

RESULTS

The median treatment duration was 4.4 years. After the full adjustment for TC, TG, HDL-C, and other major covariates, a significantly higher risk of rapid renal function decline was found in participants with higher TG [≥150 vs. <150 mg/dl, 7.7% vs. 5.5%; odds ratios (OR): 1.27; 95% confidence interval (CI): 1.06-1.51], higher TG:HDL-C ratio [≥2.7 (median) vs. <2.7, 7.7% vs. 5.0%; OR: 1.39; 95% CI: 1.14-1.71), lower TC (≥200 vs. <200 mg/dl, 6.0% vs. 7.0%; OR: 0.79; 95% CI: 0.67-0.93), or lower LDL-C levels (≥130 vs. <130 mg/dl, 6.1% vs. 7.0%; OR: 0.79; 95% CI: 0.67-0.94). Moreover, the increased risk of the primary outcome associated with elevated TG was particularly evident among individuals with lower total homocysteine levels [<12.4 (median) vs. ≥ 12.4 μmol/l, P interaction = 0.036].

CONCLUSIONS

Higher TG and TG:HDL-C ratio were independent risk factors for rapid renal function decline in hypertensive adults with normal renal function.

Serum 6-Bromotryptophan Levels Identified as a Risk Factor for CKD Progression

Background Metabolite levels reflect physiologic homeostasis and may serve as biomarkers of disease progression. Identifying metabolites associated with APOL1 risk alleles-genetic variants associated with CKD risk commonly present in persons of African descent-may reveal novel markers of CKD progression relevant to other populations.Methods We evaluated associations between the number of APOL1 risk alleles and 760 serum metabolites identified via untargeted profiling in participants of the African American Study of Kidney Disease and Hypertension (AASK) (n=588; Bonferroni significance threshold P<6.5×10^-5) and replicated findings in 678 black participants with CKD in BioMe, an electronic medical record-linked biobank. We tested the metabolite association with CKD progression in AASK, BioMe, and the Modification of Diet in Renal Disease (MDRD) Study.Results One metabolite, 6-bromotryptophan, was significant in AASK (P=4.7×10^-5) and replicated in BioMe (P=5.7×10^-3) participants, with lower levels associated with more APOL1 risk alleles. Lower levels of 6-bromotryptophan were associated with CKD progression in AASK and BioMe participants and in white participants in the MDRD Study, independent of demographics and clinical characteristics, including baseline GFR (adjusted hazard ratio per two-fold higher 6-bromotryptophan level, AASK, 0.76; 95% confidence interval [95% CI], 0.64 to 0.91; BioMe, 0.61; 95% CI, 0.43 to 0.85; MDRD, 0.52; 95% CI, 0.34 to 0.79). The interaction between the APOL1 risk alleles and 6-bromotryptophan was not significant. The identity of 6-bromotryptophan was confirmed in experiments comparing its molecular signature with that of authentic standards of other bromotryptophan isomers.Conclusions Serum 6-bromotryptophan is a consistent and novel risk factor for CKD progression.

Heart Rate Variability and Its Relation to Chronic Kidney Disease: Results From the PREVEND Study

OBJECTIVE

In the general population, reduced heart rate variability (HRV) has been associated with cardiovascular disease. However, its relation to chronic kidney disease (CKD) is debated. We therefore investigated the relation between low HRV and renal outcomes.

METHODS

In the population-based Prevention of REnal and Vascular ENdstage Disease study, renal outcomes (CKD, estimated glomerular filtration rate [eGFR], urinary albumin) were measured at baseline and three consecutive examinations. HRV measures (among which SDNN [standard deviation of normal-to-normal RR intervals]) were calculated from time series of beat-to-beat pulse wave recordings at baseline. The lowest (risk) quartile was compared with the upper three quartiles combined, in multivariable survival and linear mixed-effects analyses.

RESULTS

In 4605 participants (49% males, age range = 33-80, 0.6% blacks), we observed 341 new participants of CKD during a median follow-up duration of 7.4 years. Low SDNN was associated with higher incidence of CKD (crude HR = 1.66, 95% CI = 1.30 to 2.12, p < .001), but this association was no longer significant after adjustment for age, sex, and cardiovascular risk factors (adjusted HR = 1.13, 95% CI = 0.86 to 1.48, p = .40, similar for other HRV measures). No associations between SDNN and eGFR trajectories were found in the total sample. However, in a subgroup of participants with baseline CKD (n = 939), we found a significant association of low SDNN (but not other HRV measures) with lower baseline eGFR, even after multivariable adjustment (adjusted βlevel difference = -3.73 ml/min/1.73 m, 95% CI = -6.70 to -0.75, p = .014), but not with steeper eGFR decline.

CONCLUSIONS

These results suggest that reduced HRV may be a complication of CKD rather than a causal factor.

Reduced cortical oxygenation predicts a progressive decline of renal function in patients with chronic kidney disease

Renal tissue hypoxia is a final pathway in the development and progression of chronic kidney disease (CKD), but whether renal oxygenation predicts renal function decline in humans has not been proven. Therefore, we performed a prospective study and measured renal tissue oxygenation by blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) in 112 patients with CKD, 47 with hypertension without CKD, and 24 healthy control individuals. Images were analyzed with the twelve-layer concentric objects method that divided the renal parenchyma in 12 layers of equal thickness and reports the mean R2* value of each layer (a high R2* corresponds to low oxygenation), along with the change in R2* between layers called the R2* slope. Serum creatinine values were collected to calculate the yearly change in estimated glomerular function rate (MDRD eGFR). Follow up was three years. The change in eGFR in CKD, hypertensive and control individuals was -2.0, 0.5 and -0.2 ml/min/1.73m²/year, respectively. In multivariable regression analysis adjusted for age, sex, diabetes, RAS-blockers, eGFR, and proteinuria the yearly eGFR change correlated negatively with baseline 24 hour proteinuria and the mean R2* value of the cortical layers, and positively with the R2* slope, but not with the other covariates. Patients with CKD and high outer R2* or a flat R2* slope were three times more likely to develop an adverse renal outcome (renal replacement therapy or over a 30% increase in serum creatinine). Thus, low cortical oxygenation is an independent predictor of renal function decline. This finding should stimulate studies exploring the therapeutic impact of improving renal oxygenation on renal disease progression.

Effect of metformin on kidney function in patients with type 2 diabetes mellitus and moderate chronic kidney disease

Background

Impaired renal function can lead to the accumulation of metformin, and elevated concentrations of metformin have been associated with lactic acidosis. The aim of this study was to evaluate the effect of continuous metformin treatment in patients with type 2 diabetes mellitus (DM) and moderate chronic kidney disease (CKD) (estimated glomerular filtration rate (eGFR) 30–0 ml/min/1.73 m²) on renal function.

Methods

A total of the 616 patients were enrolled from the research database of Kaohsiung Medical University Hospital from January 1 to 2009 and December 31, 2013. The patients were divided into two groups: those who continued metformin treatment (continuation group; n = 484), and those who discontinued metformin treatment for at least 100 days (interruption group; n = 132).

Results

The slope of eGFR in the metformin interruption group was statistically lower than that in the metformin continuation group (0.75 ± 0.76 vs. –1.32 ± 0.24 mL/min/1.73 m²/year, p = 0.0007). After adjusting for baseline covariates in the multivariate linear regression analysis, the continuation of metformin (unstandardized coefficient β, –2.072; 95% confidence interval, –3.268– –0.876) was a risk factor for the patients with DM and moderate CKD.

Conclusions

Metformin may have an adverse effect on renal function in patients with type 2 DM and moderate CKD.

Overweight and Obesity Are Predictors of Progression in Early Autosomal Dominant Polycystic Kidney Disease

The association of overweight/obesity with disease progression in patients with autosomal dominant polycystic kidney disease (ADPKD) remains untested. We hypothesized that overweight/obesity associates with faster progression in early-stage ADPKD. Overall, 441 nondiabetic participants with ADPKD and an eGFR>60 ml/min per 1.73 m² who participated in the Halt Progression of Polycystic Kidney Disease Study A were categorized on the basis of body mass index (BMI; calculated using nonkidney and nonliver weight) as normal weight (18.5-24.9 kg/m²; reference; n=192), overweight (25.0-29.9 kg/m²; n=168), or obese (≥30 kg/m²; n=81). We evaluated the longitudinal (5-year) association of overweight/obesity with change in total kidney volume (TKV) by magnetic resonance imaging using linear regression and multinomial logistic regression models. Among participants, mean±SD age was 37±8 years, annual percent change in TKV was 7.4%±5.1%, and BMI was 26.3±4.9 kg/m² The annual percent change in TKV increased with increasing BMI category (normal weight: 6.1%±4.7%, overweight: 7.9%±4.8%, obese: 9.4%±6.2%; P<0.001). In the fully adjusted model, higher BMI associated with greater annual percent change in TKV (β=0.79; 95% confidence interval [95% CI], 0.18 to 1.39, per 5-unit increase in BMI). Overweight and obesity associated with increased odds of annual percent change in TKV ≥7% compared with <5% (overweight: odds ratio, 2.02; 95% CI, 1.15 to 3.56; obese: odds ratio, 3.76; 95% CI, 1.81 to 7.80). Obesity also independently associated with greater eGFR decline (slope) versus normal weight (fully adjusted β =-0.08; 95% CI, -0.15 to -0.02). In conclusion, overweight and, particularly, obesity are strongly and independently associated with rate of progression in early-stage ADPKD.

Albuminuria, Proteinuria, and Renal Disease Progression in Children with CKD

BACKGROUND AND OBJECTIVES

The role of albuminuria as an indicator of progression has not been investigated in children with CKD in the absence of diabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Children were enrolled from 49 centers of the CKD in Children study between January of 2005 and March of 2014. Cross-sectional multivariable linear regression (n=647) was used to examine the relationship between urine protein-to-creatinine (UP/C [milligrams per milligram]) and albumin-to-creatinine (ACR [milligrams per gram]) with eGFR (milliliters per minute per 1.73 m2). Parametric time-to-event analysis (n=751) was used to assess the association of UP/C, ACR, and urine nonalbumin-to-creatinine (Unon-alb/cr [milligrams per gram]) on the time to the composite endpoint of initiation of RRT or 50% decline in eGFR.

RESULTS

The median follow-up time was 3.4 years and 202 individuals experienced the event. Participants with a UP/C≥0.2 mg/mg and ACR≥30 mg/g had a mean eGFR that was 16 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. Individuals with ACR<30 mg/g, but a UP/C≥0.2 mg/mg, had a mean eGFR that was 9.3 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. When categories of ACR and Unon-alb/cr were created on the basis of clinically meaningful cutoff values of UP/C with the same sample sizes for comparison, the relative times (RTs) to the composite end-point were almost identical when comparing the middle (RT=0.31 for UP/C [0.2-2.0 mg/mg], RT=0.38 for ACR [56-1333 mg/g], RT=0.31 for Unon-alb/cr [118-715 mg/g]) and the highest (RT=0.08 for UP/C [>2.0 mg/mg], RT=0.09 for ACR [>1333 mg/g], RT=0.07 for Unon-alb/cr [>715 mg/g]) levels to the lowest levels. A similar trend was seen when categories were created on the basis of clinically meaningful cutoff values of ACR (<30, 30-300, >300 mg/g).

CONCLUSIONS

In children with CKD without diabetes, the utility of an initial UP/C, ACR, and Unon-alb/cr for characterizing progression is similar.

Comparison between Different Measures of Body Fat with Kidney Function Decline and Incident CKD

BACKGROUND AND OBJECTIVES

Although anthropometric measures of body fat are associated with development of CKD, they may not be able to distinguish between various forms of fat and therefore may be less accurate than computed tomography (CT) measures. We compared the association of CT and anthropometric measures of obesity with kidney outcomes in the Health Aging and Body Composition Study.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Participants were recruited from March of 1997 through July of 1998. CT measures included visceral abdominal fat (VAT), subcutaneous adipose tissue (SAT), and intermuscular fat area (IMAT), whereas anthropometric measures included waist circumference (WC) and body mass index (BMI). Kidney outcomes included kidney function (KF) decline (30% decrease in eGFRcysC in follow-up at either year 3 or 10) or incident CKD (follow-up eGFRcysC≤60 ml/min per 1.73 m2 in individuals with baseline GFR>60 ml/min per 1.73 m2). Multivariable logistic regression models and Poisson regression models were used to evaluate the association with decline in KF and incident kidney disease, respectively. We also assessed for the independent associations among the exposure measures by including them in the same model.

RESULTS

Two-thousand four-hundred and eighty-nine individuals were included. Mean age was 74±3 years, 49% were men, 39% were black, 59% were hypertensive, and 15% were diabetic. KF decline occurred in 17% of the population, whereas incident CKD also occurred in 17% of those at risk. In continuous models, SAT, VAT, IMAT, BMI, and WC (per SD increase) were all significantly associated with KF decline. There was a significant interaction between VAT and CKD with regard to KF decline (P=0.01). Only VAT, BMI, and WC were associated with incident CKD. Only VAT remained a significant risk factor for incident CKD when other exposure variables were included in the same model. There was no association between any measure of obesity and kidney outcomes when creatinine values at years 3 and 10 were used to estimate changes in eGFR.

CONCLUSIONS

Anthropometric measures of body fat appear to provide as consistent estimates of KF decline risk as CT measures in elders.