Diagnostic accuracy of cystatin C compared to serum creatinine for the estimation of renal dysfunction in adults and children--a meta-analysis

Plasma D-asparagine and the D/L-serine ratio reflect chronic kidney diseases in children regardless of physique

Biomarkers that accurately reflect renal function are essential in management of chronic kidney diseases (CKD). However, in children, age/physique and medication often alter established renal biomarkers. We studied whether amino acid enantiomers in body fluids correlate with renal function and whether they are influenced by physique or steroid medication during development. We conducted a prospective study of children 2 to 18 years old with and without CKD. We analyzed associations of serine/asparagine enantiomers in body fluids with major biochemical parameters as well as physique. To study consequences of kidney dysfunction and steroids on serine/asparagine enantiomers, we generated juvenile mice with uninephrectomy, ischemic reperfusion injury, or dexamethasone treatment. We obtained samples from 27 children, of which 12 had CKD due to congenital (n = 7) and perinatal (n = 5) causes. Plasma D-asparagine and the D/L-serine ratio had robust, positive linear associations with serum creatinine and cystatin C, and detected CKD with high sensitivity and specificity, uninfluenced by body size or biochemical parameters. In the animal study, kidney dysfunction increased plasma D-asparagine and the D/L-serine ratio, but dexamethasone treatment did not. Thus, plasma D-asparagine and the D/L-serine ratio can be useful markers for renal function in children.

Estimated glomerular filtration rate in clinical practice: Consensus positioning of the Brazilian Society of Nephrology (SBN) and Brazilian Society of Clinical Pathology and Laboratory Medicine (SBPC/ML)

Chronic kidney disease (CKD) represents one of today's main public health problems. Serum creatinine measurement and estimation of the glomerular filtration rate (GFR) are the main tools for evaluating renal function. There are several equations to estimate GFR, and CKD-EPI equation (Chronic Kidney Disease - Epidemiology) is the most recommended one. There are still some controversies regarding serum creatinine measurement and GFR estimation, since several factors can interfere in this process. An important recent change was the removal of the correction for race from the equations for estimating GFR, which overestimated kidney function, and consequently delayed the implementation of treatments such as dialysis and kidney transplantation. In this consensus document from the Brazilian Societies of Nephrology and Clinical Pathology and Laboratory Medicine, the main concepts related to the assessment of renal function are reviewed, as well as possible existing controversies and recommendations for estimating GFR in clinical practice.

A molecular index for biological age identified from the metabolome and senescence-associated secretome in humans

Unlike chronological age, biological age is a strong indicator of health of an individual. However, the molecular fingerprint associated with biological age is ill-defined. To define a high-resolution signature of biological age, we analyzed metabolome, circulating senescence-associated secretome (SASP)/inflammation markers and the interaction between them, from a cohort of healthy and rapid agers. The balance between two fatty acid oxidation mechanisms, β-oxidation and ω-oxidation, associated with the extent of functional aging. Furthermore, a panel of 25 metabolites, Healthy Aging Metabolic (HAM) index, predicted healthy agers regardless of gender and race. HAM index was also validated in an independent cohort. Causal inference with machine learning implied three metabolites, β-cryptoxanthin, prolylhydroxyproline, and eicosenoylcarnitine as putative drivers of biological aging. Multiple SASP markers were also elevated in rapid agers. Together, our findings reveal that a network of metabolic pathways underlie biological aging, and the HAM index could serve as a predictor of phenotypic aging in humans.

The rationale for nephron-sparing surgery in unilateral non-syndromic Wilms tumour

The central question of nephron-sparing surgery in unilateral non-syndromic Wilms tumour sits at a crossroads between surgery, oncology, and nephrology. There has been a significant paradigm shift in paediatric oncology towards reducing toxicity and addressing long-term treatment-related sequalae amongst childhood cancer survivors. After paediatric nephrectomy and 30-50 years of follow-up, 40% of patients will have chronic kidney disease, including 22% with hypertension and 23% with albuminuria. It is difficult to predict which patients will progress to develop hypertension, reduced glomerular filtration rate, albuminuria, and a higher cardiovascular risk. For these reasons, nephron-sparing surgery when it is technically feasible must be considered. To decrease the incidence of positive surgical margins (viable tumour present at a resection margin), incomplete lymph node sampling, and complications, these procedures should be performed at specialist and experienced reference centres. Based on the impacts of individual treatment pathways, survivors of childhood WT need to be followed through adulthood for early detection of chronic kidney disease, hypertension, and prevention of cardiovascular events.

Renal Congestion in Heart Failure: Insights in Novel Diagnostic Modalities

Heart failure is increasingly prevalent and is estimated to increase its burden in the following years. A well-reported comorbidity of heart failure is renal dysfunction, where predominantly changes in the patient's volume status, tubular necrosis or other mechanical and neurohormonal mechanisms seem to drive this impairment. Currently, there are established biomarkers evaluating the patient's clinical status solely regarding the cardiovascular or renal system. However, as the coexistence of heart and renal failure is common and related to increased mortality and hospitalization for heart failure, it is of major importance to establish novel diagnostic techniques, which could identify patients with or at risk for cardiorenal syndrome and assist in selecting the appropriate management for these patients. Such techniques include biomarkers and imaging. In regards to biomarkers, several peptides and miRNAs indicative of renal or tubular dysfunction seem to properly identify patients with cardiorenal syndrome early on in the course of the disease, while changes in their serum levels can also be helpful in identifying response to diuretic treatment. Current and novel imaging techniques can also identify heart failure patients with early renal insufficiency and assess the volume status and the effect of treatment of each patient. Furthermore, by assessing the renal morphology, these techniques could also help identify those at risk of kidney impairment. This review aims to present all relevant clinical and trial data available in order to provide an up-to-date summary of the modalities available to properly assess cardiorenal syndrome.

Eliminating the need for preoperative intravenous hyperhydration: Sodium thiosulfate as nephrotoxicity prevention in HIPEC-treated patients - A retrospective analysis

BACKGROUND

Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC) is an effective treatment for peritoneal metastases. However, HIPEC with cisplatin is associated with renal toxicity. Sodium thiosulfate (ST) has been shown to prevent cisplatin-induced toxicity.

METHODS

A retrospective, single-center analysis of patients treated curatively for peritoneal surface malignancy, who underwent cytoreductive surgery with cisplatin-based HIPEC between 2015 and 2020. Patients were categorized into three groups based on the management of cisplatin-induced renal toxicity: preoperative hyperhydration alone (PHH), preoperative hyperhydration with ST (PHH + ST), and ST alone. Renal function and complications, in terms of Acute (AKI) and chronic kidney injury (CKI), were monitored and analyzed during 3 postoperative months.

RESULTS

This study included 220 consecutive patients. Mean serum creatinine levels were 95, 57 and 61 mmol/L, for PHH, PHH + ST and ST groups, respectively (p < 0.001). Glomerular Filtration Rate (GFR) were 96, 94 and 78 ml/min/1.73 m2, respectively (p < 0.001). AKI and CKI are respectively for PHH, PHH + ST and ST groups were 21 % (n = 46), 1 % (n = 2) and 0 % vs 19 % (n = 42), 0 % and 0 % (p < 0.001), for pairwise analysis did not show any difference between PHH + ST and ST alone combination, regarding nephrological outcomes. All patients were followed 3 months postoperatively.

CONCLUSION

There is no need for preoperative hyperhydration when sodium-thiosulfate is used to prevent cisplatin-induced nephrotoxicity in patients undergoing cytoreductive surgery with HIPEC. These findings have implications for improving and simplifying the management of patients with peritoneal metastases undergoing HIPEC with cisplatin.

Implication of MAPK, Lipocalin-2, and Fas in the protective action of liposomal resveratrol against isoproterenol-induced kidney injury

Background and Objective

Isoproterenol (ISO) is a non-selective β-adrenergic receptor agonist. It can be used to treat bradycardia and cardiogenic shock. Despite its usefulness, the overstimulation of β-receptors by ISO can cause "cardiorenal syndrome," a term used to describe heart and kidney damage. Resveratrol (RES), a natural polyphenol, has marked anti-inflammatory and antioxidant activities. The present work was designed to study the protective efficacy of liposomal resveratrol (L-RES) against ISO-induced kidney injury.

Materials and Methods

The kidney injury was induced in rats by administering ISO (50 mg/kg, s.c.) twice a week for 2 weeks. RES and L-RES were administered at a dose (20 mg/kg/ day, p.o.) along with ISO for 2 weeks. Inflammatory and apoptotic biomarkers were analyzed, which were validated using histochemical analysis.

Results

ISO caused renal dysfunction, which manifested as elevated urea, creatinine and uric acid, besides cystatin c and MAPK protein overexpression. In addition, ISO induced gene expression of Fas and lipocalin-2 and provoked genomic DNA fragmentation in renal tissues as compared with the control group. Histological examination confirmed morphological alterations of the kidney tissues obtained from the ISO group. Concurrent treatment of either RES or L-RES with ISO significantly ameliorated kidney damage as demonstrated by the improvement of all measured parameters with the best results for L-RES. The histopathological findings were correlated with the above biochemical parameters.

Conclusion

L-RES could be a promising approach for the prevention of kidney injury induced by ISO, most likely via the downregulation of MAPK, cystatin c, Fas, and lipocalin-2.

Current Status of Protein Biomarkers in Urolithiasis-A Review of the Recent Literature

Urolithiasis is an increasingly common clinical problem worldwide. The formation of stones is a combination of metabolic status, environmental factors, family history and many other aspects. It is important to find new ways to quickly detect and assess urolithiasis because it causes sudden, severe pain and often comes back. One way to do this is by exploring new biomarkers. Current advances in proteomic studies provide a great opportunity for breakthroughs in this field. This study focuses on protein biomarkers and their connection to kidney damage and inflammation during urolithiasis.

A magnetic solid phase chemiluminescent immunoassay for quantification of Cystatin C in human serum

A chemiluminescent immunoassay for human serum Cystatin C (Cys C) was established using a direct-antibody sandwich model. The immunoassay kit uses magnetic separation technology, using magnetic particles as the reaction solid phase, alkaline phosphatase as the marker enzyme, and a new chemiluminescent substrate APLS as the substrate. It has the characteristics of high sensitivity and short reaction time. This product uses high-affinity antibodies, resulting in a high specificity. The established method showed good accuracy, uniformity, and stability. The limit of detection was 2.39 ng/mL. The intra-assay coefficient of variation (CV) was 3.36%-6.00%, the interassay CV was 4.12%-5.35%, and the recovery rate was 99.07%. The correlation coefficient (r) of Cys-C kit was 0.999388 ≥ 0.9900. The accuracy of the developed method was tested by automatic chemiluminescence instrument (P > 0.05). The lowest titer was 0.92500, and the highest was 1.10000. The developed method showed a good correlation with the product from Roche by comparing these two kits in 240 clinical samples from China. In total, 1392 clinical patient from China samples were measured using the reagent kit developed in this study.

The Impact of Acute Nutritional Interventions on the Plasma Proteome

CONTEXT

Humans respond profoundly to changes in diet, while nutrition and environment have a great impact on population health. It is therefore important to deeply characterize the human nutritional responses.

OBJECTIVE

Endocrine parameters and the metabolome of human plasma are rapidly responding to acute nutritional interventions such as caloric restriction or a glucose challenge. It is less well understood whether the plasma proteome would be equally dynamic, and whether it could be a source of corresponding biomarkers.

METHODS

We used high-throughput mass spectrometry to determine changes in the plasma proteome of i) 10 healthy, young, male individuals in response to 2 days of acute caloric restriction followed by refeeding; ii) 200 individuals of the Ely epidemiological study before and after a glucose tolerance test at 4 time points (0, 30, 60, 120 minutes); and iii) 200 random individuals from the Generation Scotland study. We compared the proteomic changes detected with metabolome data and endocrine parameters.

RESULTS

Both caloric restriction and the glucose challenge substantially impacted the plasma proteome. Proteins responded across individuals or in an individual-specific manner. We identified nutrient-responsive plasma proteins that correlate with changes in the metabolome, as well as with endocrine parameters. In particular, our study highlights the role of apolipoprotein C1 (APOC1), a small, understudied apolipoprotein that was affected by caloric restriction and dominated the response to glucose consumption and differed in abundance between individuals with and without type 2 diabetes.

CONCLUSION

Our study identifies APOC1 as a dominant nutritional responder in humans and highlights the interdependency of acute nutritional response proteins and the endocrine system.

Clinical significance of serum cystatin C-to-creatinine ratio as a surrogate marker for incident osteoporotic fracture predictions

Background

Detection of appropriate indicators is valuable for preventing incidental osteoporotic fractures. We statistically evaluated the significance of serum cystatin C-to-creatinine ratio (CysC/Cr) as a surrogate marker for incident major osteoporotic fractures (MOF) prediction.

Methods

Eligible patients with simultaneous measurement of CysC/Cr and bone mineral density in the lumbar spine and proximal femur were selected, and their fracture histories until 5 years after baseline were observed in the retrospective area cohort data. Patients who were followed up until termination or the first osteoporotic fracture were included, and loss of follow-up or death was excluded. Candidate risk factors for osteoporotic fractures were tested for risk ratios using a cox regression analysis. Receiver operating characteristic tests were performed on factors with significantly higher risk ratios and evaluated with Kaplan-Meier survival analysis to determine the hazard ratios of the factors.

Results

A total of 175 patients of whom 28 had incident MOF, 38 men, and 137 women, were enrolled. The mean age was 70.2 years. A significantly higher risk ratio was shown in the presence of prevalent MOF, hyper fall-ability, lifestyle-related diseases, chronic kidney diseases ≥ Grade3a, and higher CysC/Cr. All parameters had cutoff indices and showed significantly higher hazard ratios.

Conclusions

These results suggested that CysC/Cr may be a predictive marker of incident osteoporotic fractures. It might work as a screening tool for MOF risk.

Optimizing Vancomycin Therapy in Critically Ill Children: A Population Pharmacokinetics Study to Inform Vancomycin Area under the Curve Estimation Using Novel Biomarkers

Area under the curve (AUC)-directed vancomycin therapy is recommended, but Bayesian AUC estimation in critically ill children is difficult due to inadequate methods for estimating kidney function. We prospectively enrolled 50 critically ill children receiving IV vancomycin for suspected infection and divided them into model training (n = 30) and testing (n = 20) groups. We performed nonparametric population PK modeling in the training group using Pmetrics, evaluating novel urinary and plasma kidney biomarkers as covariates on vancomycin clearance. In this group, a two-compartment model best described the data. During covariate testing, cystatin C-based estimated glomerular filtration rate (eGFR) and urinary neutrophil gelatinase-associated lipocalin (NGAL; full model) improved model likelihood when included as covariates on clearance. We then used multiple-model optimization to define the optimal sampling times to estimate AUC24 for each subject in the model testing group and compared the Bayesian posterior AUC24 to AUC24 calculated using noncompartmental analysis from all measured concentrations for each subject. Our full model provided accurate and precise estimates of vancomycin AUC (bias 2.3%, imprecision 6.2%). However, AUC prediction was similar when using reduced models with only cystatin C-based eGFR (bias 1.8%, imprecision 7.0%) or creatinine-based eGFR (bias -2.4%, imprecision 6.2%) as covariates on clearance. All three model(s) facilitated accurate and precise estimation of vancomycin AUC in critically ill children.

Recent Developments in the Evaluation and Management of Cardiorenal Syndrome: A Comprehensive Review

Cardiorenal syndrome (CRS) is an increasingly recognized diagnostic entity associated with high morbidity and mortality among acutely ill heart failure (HF) patients with acute and/ or chronic kidney diseases (CKD). While traditionally viewed as a state of decline in glomerular filtration rate (GFR) due to decreased renal perfusion, mainly due to therapeutic interventions to relieve congestive in HF, recent insights into the underlying pathophysiologic mechanisms of CRS led to a broader definition and further classification of CRS into 5 distinct types. In this comprehensive review, we discuss the classification of CRS, highlighting the underlying common pathogenetic pathways of heart failure and kidney injury, including increased congestion, neurohormonal dysregulation, oxidative stress as well as inflammation, and cytokine storm that are particularly evident in COVID-19 patients with multiorgan failure and also in those with other disorders including sepsis, systemic lupus erythematosus and amyloidosis. In this review we also present the recent advances in the diagnostic strategies of CRS including cardiac and renal biomarkers as well as advanced cardiac and renal imaging techniques that are available to aid in the diagnosis as well as in the prognostication of this disorder. Finally, we discuss the various therapeutic options available to-date, including fluid optimization, hemofiltration, renal replacement therapy as well as the role of SGLT2 inhibitors in light of recent data from RCTs. It is important to note that, CRS population are either excluded or underrepresented, at best, in major RCTs and therefore, therapeutic recommendations are largely extrapolated from HF and CKD clinical trials.

Estimated glomerular filtration rates are higher when creatinine-based equations are compared with a cystatin C-based equation in coronavirus disease 2019

OBJECTIVES

Estimations of glomerular filtration rate (eGFR) are based on analyses of creatinine and cystatin C, respectively. Coronavirus disease 2019 (COVID-19) patients in the intensive care unit (ICU) often have acute kidney injury (AKI) and are at increased risk of drug-induced kidney injury. The aim of this study was to compare creatinine-based eGFR equations to cystatin C-based eGFR in ICU patients with COVID-19.

METHODS

After informed consent, we included 370 adult ICU patients with COVID-19. Creatinine and cystatin C were analyzed at admission to the ICU as part of the routine care. Creatinine-based eGFR (ml/min) was calculated using the following equations, developed in chronological order; the Cockcroft-Gault (C-G), Modified Diet in Renal Disease (MDRD)1999, MDRD 2006, Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), and Lund-Malmö revised (LMR) equations, which were compared with eGFR calculated using the cystatin C-based Caucasian Asian Pediatric Adult (CAPA) equation.

RESULTS

The median eGFR when determined by C-G was 99 ml/min and interquartile range (IQR: 67 ml/min). Corresponding estimations for MDRD1999 were 90 ml/min (IQR: 54); MDRD2006: 85 ml/min (IQR: 51); CKD-EPI: 91 ml/min (IQR: 47); and for LMR 83 ml/min (IQR: 41). eGFR was calculated using cystatin C and the CAPA equation value was 70 ml/min (IQR: 38). All differences between creatinine-based eGFR versus cystatin C-based eGFR were significant (p < .00001).

CONCLUSIONS

Estimation of GFR based on various analyses of creatinine are higher when compared with a cystatin C-based equation. The C-G equation had the worst performance and should not be used in combination with modern creatinine analysis methods for determination of drug dosage in COVID-19 patients.

Role of serum cystatin C in the prediction of acute kidney injury following pediatric cardiac surgeries: A single center experience

Intense contemporary research is directed towards validating novel biomarkers to predict acute kidney injury (AKI) in children undergoing cardiothoracic surgeries. We aimed to evaluate the role of cystatin C in early prediction of AKI following cardiac surgery in children with congenital heart disease. Prospective observational cohort study was conducted on 40 children with congenital heart disease undergoing cardiac surgery. 40 healthy children with matched age and sex were enrolled as a control group. Children were subjected to physical examination, routine blood tests, echocardiography, and measurement of plasma cystatin C level on different occasions. The median age of the patients was 3.65 years, a range from 1 to 5 years with no significant difference regarding the age and sex of cases and control groups. The mean serum cystatin C level in patients was 0.75 ± 0.15, 1.35 ± 0.34 and 1.21 ± 0.38 mg/dL (preoperative, at 6 h and at 24 h postoperative, respectively) with statistically significant difference P < .05. 30% of the patients developed postoperative AKI with significantly higher serum cystatin C at 6 hours postoperative >1.33 mg/dL compared to preoperative level p P < .05. Serum cystatin C level was positively correlated with cardiac bypass time, ischemic time and length of hospital stay at 6 hours postoperative. Serum cystatin C is a sensitive marker for early detection of AKI following cardiac surgery in children with congenital heart disease and it was positively correlated with cardiac bypass time, ischemic time and length of hospital stay.

Heart Failure and Cardiorenal Syndrome: A Narrative Review on Pathophysiology, Diagnostic and Therapeutic Regimens-From a Cardiologist's View

In cardiorenal syndrome (CRS), heart failure and renal failure are pathophysiologically closely intertwined by the reciprocal relationship between cardiac and renal injury. Type 1 CRS is most common and associated with acute heart failure. A preexistent chronic kidney disease (CKD) is common and contributes to acute kidney injury (AKI) in CRS type 1 patients (acute cardiorenal syndrome). The remaining CRS types are found in patients with chronic heart failure (type 2), acute and chronic kidney diseases (types 3 and 4), and systemic diseases that affect both the heart and the kidney (type 5). Establishing the diagnosis of CRS requires various tools based on the type of CRS, including non-invasive imaging modalities such as TTE, CT, and MRI, adjuvant volume measurement techniques, invasive hemodynamic monitoring, and biomarkers. Albuminuria and Cystatin C (CysC) are biomarkers of glomerular filtration and integrity in CRS and have a prognostic impact. Comprehensive "all-in-one" magnetic resonance imaging (MRI) approaches, including cardiac magnetic resonance imaging (CMR) combined with functional MRI of the kidneys and with brain MRI are proposed for CRS. Hospitalizations due to CRS and mortality are high. Timely diagnosis and initiation of effective adequate therapy, as well as multidisciplinary care, are pertinent for the improvement of quality of life and survival. In addition to the standard pharmacological heart failure medication, including SGLT2 inhibitors (SGLT2i), renal aspects must be strongly considered in the context of CRS, including control of the volume overload (diuretics) with special caution on diuretic resistance. Devices involved in the improvement of myocardial function (e.g., cardiac resynchronization treatment in left bundle branch block, mechanical circulatory support in advanced heart failure) have also shown beneficial effects on renal function.

Gestational and Age-Specific Cystatin C Reference Intervals for Newborns

OBJECTIVE

Cystatin C (CysC) references are useful for the monitoring of renal function in neonates. However, the standard CysC references in newborn infants have not been determined. The aim of this study was to establish a useful reference range for CysC in newborns.

STUDY DESIGN

Serum CysC levels were measured in 1,919 blood samples from 1,044 newborns during their first 28 days of life. CysC levels were analyzed for associations between subgroups dichotomized by postnatal age (PA) and gestational age (GA). The serum CysC reference intervals were determined according to the PA and GA. The associations between the serum CysC level and other biochemical parameters as well as perinatal factors were also analyzed.

RESULTS

In this study, the mean GA was 35.8 ± 2.9 weeks and the birth weight (BW) was 2,614 ± 697 g. Reference ranges of serum CysC were determined, and a general decreasing trend of CysC levels was observed as the GA increased. CysC levels differed significantly among the PA and GA categories (p < 0.001). Serum CysC levels were relatively stable throughout the GA range but were impacted by the white blood cell count within the first postnatal 24 hours. Moreover, CysC levels always correlated positively with serum creatinine concentrations (p < 0.001). Serum Cr levels were influenced by multiple factors, including BW, GA, total bilirubin, direct bilirubin, white blood cell count, C-reactive protein, and blood urea nitrogen.

CONCLUSION

Reference levels of serum CysC should be determined according to the PA and GA. In contrast to Cr, serum CysC is a reliable index for assessing renal function in neonates as it is influenced by very few factors. The CysC reference levels will allow neonatologists to accurately evaluate renal function in the neonatal population.

KEY POINTS

· Cystatin C is a useful marker of the glomerular filtration rate in neonates.. · A reference range for cystatin C using 1,919 blood samples of 1,044 newborns was determined.. · In contrast to creatinine, only a few nonrenal factors influence serum cystatin C..

Differential Bias for Creatinine- and Cystatin C- Derived Estimated Glomerular Filtration Rate in Critical COVID-19

COVID-19 is a systemic disease, frequently affecting kidney function. Dexamethasone is standard treatment in severe COVID-19 cases, and is considered to increase plasma levels of cystatin C. However, this has not been studied in COVID-19. Glomerular filtration rate (GFR) is a clinically important indicator of renal function, but often estimated using equations (eGFR) based on filtered metabolites. This study focuses on sources of bias for eGFRs (mL/min) using a creatinine-based equation (eGFRLMR) and a cystatin C-based equation (eGFRCAPA) in intensive-care-treated patients with COVID-19. This study was performed on 351 patients aged 18 years old or above with severe COVID-19 infections, admitted to the intensive care unit (ICU) in Uppsala University Hospital, a tertiary care hospital in Uppsala, Sweden, between 14 March 2020 and 10 March 2021. Dexamethasone treatment (6 mg for up to 10 days) was introduced 22 June 2020 (n = 232). Values are presented as medians (IQR). eGFRCAPA in dexamethasone-treated patients was 69 (37), and 74 (46) in patients not given dexamethasone (p = 0.01). eGFRLMR was not affected by dexamethasone. eGFRLMR in females was 94 (20), and 75 (38) in males (p = 0.00001). Age and maximal CRP correlated negatively to eGFRCAPA and eGFRLMR, whereas both eGFR equations correlated positively to BMI. In ICU patients with COVID-19, dexamethasone treatment was associated with reduced eGFRCAPA. This finding may be explained by corticosteroid-induced increases in plasma cystatin C. This observation is important from a clinical perspective since adequate interpretation of laboratory results is crucial.

New aspects in cardiorenal syndrome and HFpEF

Cardiorenal syndrome (CRS) is a complex disease in which the heart and kidneys are simultaneously affected, and subsequently, the malfunction of one organ promotes the deterioration of the other. Heart failure (HF) with preserved ejection fraction (HFpEF) is the most common form of HF. The pathophysiology of CRS is not well known and several mechanisms have been proposed. An elevation of central venous pressure seems to be one of the key points to consider, among others such as an increase in intraabdominal pressure. Several diagnostic tools have been identified to establish the diagnosis of CRS in patients with HFpEF. Currently, the availability of biomarkers of renal and cardiac injury, the use of pulmonary ultrasound, the monitoring of the size of the inferior vena cava and the study of the renal venous pattern offer a new dimension in accurately diagnosing and quantifying organ damage in CRS. Beyond the symptomatic treatment of congestion, until recently specific therapeutic tools for patients with CRS and HFpEF were not available. Interestingly, the development of new drugs such as the angiotensin/neprilysin inhibitors and sodium-glucose cotransporter-2 (SGLT-2) inhibitors offer new therapeutic strategies with potential benefits in reduction of cardiorenal adverse outcomes in this population. Randomized clinical trials that focus on patients with HFpEF are currently ongoing to delineate optimal new treatments that may be able to modify their prognosis. In addition, multidisciplinary teamwork (nephrologist, cardiologist and nurse) is expected to decrease the number of visits and the rate of hospitalizations, with a subsequent patient benefit.

Circulating Cystatin C Is an Independent Risk Marker for Cardiovascular Outcomes, Development of Renal Impairment, and Long-Term Mortality in Patients With Stable Coronary Heart Disease: The LIPID Study

Background

Elevated plasma cystatin C levels reflect reduced renal function and increased cardiovascular risk. Less is known about whether the increased risk persists long‐term or is independent of renal function and other important biomarkers.

Methods and Results

Cystatin C and other biomarkers were measured at baseline (in 7863 patients) and 1 year later (in 6106 patients) in participants in the LIPID (Long‐Term Intervention with Pravastatin in Ischemic Disease) study, who had a previous acute coronary syndrome. Outcomes were ascertained during the study (median follow‐up, 6 years) and long‐term (median follow‐up, 16 years). Glomerular filtration rate (GFR) was estimated using Chronic Kidney Disease Epidemiology Collaboration equations (first GFR‐creatinine, then GFR‐creatinine‐cystatin C). Over 6 years, in fully adjusted multivariable time‐to‐event models, with respect to the primary end point of coronary heart disease mortality or nonfatal myocardial infarction, for comparison of Quartile 4 versus 1 of baseline cystatin C, the hazard ratio was 1.37 (95% CI, 1.07–1.74; P=0.01), and for major cardiovascular events was 1.47 (95% CI, 1.19–1.82; P<0.001). Over 16 years, the association of baseline cystatin C with coronary heart disease, cardiovascular, and all‐cause mortality persisted (each P<0.001) and remained significant after adjustment for estimated GFR‐creatinine‐cystatin C. Cystatin C also predicted the development of chronic kidney disease for 6 years (odds ratio, 6.61; 95% CI, 4.28–10.20) independently of estimated GFR‐creatinine and other risk factors. However, this association was no longer significant after adjustment for estimated GFR‐creatinine‐cystatin C.

Conclusions

Cystatin C independently predicted major cardiovascular events, development of chronic kidney disease, and cardiovascular and all‐cause mortality. Prediction of long‐term mortality was independent of improved estimation of GFR.

Registration

URL: https://anzctr.org.au; Unique identifier: ACTRN12616000535471.

Cystatin C Concentration During the First Three Postnatal Days in Healthy Term Newborns

OBJECTIVE

Cystatin C (Cys-C) concentration has not been examined sufficiently among healthy newborn population, particularly in terms of reference values. This study aimed to establish gender-, postnatal age- and birth weight-specific Cys-C concentration for healthy term newborns. Its objective was also to examine if there were any differences between our measured concentration and the reference interval established by the CALIPER study.

METHODS

Serum samples from a total of 90 healthy term newborns were used to determine Cys-C concentration. Cys-C was measured within first three days of birth using particle-enhanced turbidimetric immunoassay (PETIA) on the Architect plus ci8200 analyzer.

RESULTS

Median concentration of the Cys-C was 2.05 mg/L. There were no statistically significant differences in Cys-C concentration regarding gender (p=0.779), birth weight (p=0.505), postnatal age (p=0.512) or Apgar score (p=0.799). The value of the 2.5th and 97.5th percentile for Cys-C concentrations for girls was 0.93-3.15 mg/L and for boys it was 1.5-3.36 mg/L.

CONCLUSION

Cys-C concentration in healthy term newborns does not depend on gender, birth weight, postnatal age, or Apgar score. Our measured concentration range of CyS-C in healthy newborns turned out to be slightly wider than the interval determined in the CALIPER study.

Biomarkers of acute kidney injury in pediatric cardiac surgery

Acute kidney injury (AKI) is characterized by a sudden decrease in kidney function. Children with congenital heart disease are a special group at risk of developing AKI. We performed a systematic review of the literature to search for studies reporting the usefulness of novel urine, serum, and plasma biomarkers in the diagnosis and progression of AKI and their association with clinical outcomes in children undergoing pediatric cardiac surgery. In thirty studies, we analyzed the capacity to predict AKI and poor outcomes of five biomarkers: Cystatin C, Neutrophil gelatinase-associated lipocalin, Interleukin-18, Kidney injury molecule-1, and Liver fatty acid-binding protein. In conclusion, we suggest the need for further meta-analyses with the availability of additional studies.

Cystatin and Glomerular Filtration Rate in Obese Versus Non-obese Adolescents

Background: Obesity is well known as an independent risk factor for chronic kidney disease. Thus meticulous assessment of renal function is more essential in obese individuals. Glomerular filtration rate (GFR) is commonly estimated based on serum creatinine (Cr).  However, using Cr as marker of kidney function has some limitations and Cystatin C has been reported as an alternative marker. Aim of work: This study was designed to assess renal function using both GFR and cystatin in obese adolescents. Methods: This case-control study enrolled ninety Egyptian adolescents aged between 10 and 18 years old who were divided equally into two groups according to body mass index (obese and non-obese).  Each participant was subjected to full medical history taking, anthropometric measures, and Laboratory investigation including CBC, serum Cr, estimated GFR and cystatin C. Results:  Serum Cr level was significantly higher in obese adolescents compared to non-obese mean value (0.94) and (0.79) resepectively. Also, eGFR based on Cr was significantly lower in obese group compared to controls (73.1) and ( (85.30)respectively. Cystatin C showed non-significant higher levels in obese group versus controls with mean value (2.28) and (1.85)respectively. Cystatin C at Cut-off value of 1.525 and 95% CI showed sensitivity of 47.2% and specificity of 63.9% for evaluation of kidney affection in obese children and adolescences. Conclusion: GFR is affected in obese adolescence with elevation of serum creatinine and unexpected non significant elevation of cystatin C in obese adolescence when compared by control group. Keywords: Cystatin, Creatinine, Pediatric obesity, GFR, renal function.

Assessment of cystatin C in pediatric sickle cell disease and β-thalassemia as a marker of subclinical cardiovascular dysfunction: a case-control study

Cardiovascular complications represent the main determinant of survival in patients with hemoglobinopathies. Serum cystatin C is a well-known marker of nephropathy in sickle cell disease (SCD) and β-thalassemia patients that has recently emerged as a strong predictor of cardiovascular dysfunction in patients with and without kidney disease. We performed a case control study to determine the role of cystatin C as a predictor of subclinical cardiovascular dysfunction in SCD and β-thalassemia patients. We enrolled 40 SCD patients with a mean age of 12.4 years, 40 β-thalassemia patients with a mean age of 11.4 years and 40 age and sex-matched controls. We assessed hematological profile, serum ferritin, urinary albumin-creatinine ratio (UACR), serum cystatin C, echocardiography and carotid intima media thickness (CIMT). UACR, cystatin C and CIMT were higher in SCD and β-thalassemia patients compared to controls (p < .001). Significantly higher cystatin C levels were observed in SCD and β-thalassemia patients with nephropathy or left ventricular systolic dysfunction (shortening fraction <30%, or ejection fraction <55%; p < .001). Moreover, SCD patients with pulmonary hypertension had significantly higher cystatin C levels. Cystatin C levels were positively correlated with CIMT in SCD (p = .02) and β-thalassemia patients (p < .001) while negatively correlated with ejection fraction and shortening fraction (p < .001). The cutoff values of cystatin C ≥ 16.03 and ≥ 13.2 (ng/mL) could detect subclinical cardiac dysfunction risk among SCD and β-thalassemia patients respectively. Cystatin C appears to be a promising marker for subclinical cardiovascular dysfunction in SCD and β-thalassemia patients.

Estimation of kidney function in patients with primary neuromuscular diseases: is serum cystatin C a better marker of kidney function than creatinine?

BACKGROUND

Using serum creatinine leads to an overestimation of kidney function in patients with primary neuromuscular disorders, and reduced kidney function may remain undetected. Cystatin C (CysC) could provide a better estimation.

AIM

To evaluate the precision, accuracy, and bias of two creatinine-, one cystatin C-based and one combined equation to estimate glomerular filtration rate (eGFR) in patients with primary neuromuscular disease.

PATIENTS AND METHODS

Of the 418 patients initially identified at the out-patient clinic, data on kidney function was obtained for 145 adult patients (age 46 ± 14 years, BMI 26 ± 6 kg/m²) with primary neuromuscular disease. Kidney function was measured by iohexol clearance, and blood samples for serum creatinine and CysC were drawn simultaneously. Bias was defined as the mean difference between eGFR and measured iohexol clearance, and accuracy as the proportion of eGFRs within ± 10% (P10) of measured clearance.

RESULTS

Kidney function (iohexol clearance) was 81 ± 19 (38-134) ml/min/1.73m². All equations overestimated kidney function by 22-60 ml/min/1.73m². eGFR CysC had the lowest bias overall 22 (95% CI 20-26) ml/min/1.73m² also at all levels of kidney function we evaluated (at 30-59 ml/min/1.73m² bias was 27 (95% CI 21-35), at 60-89 it was 25 (95% CI 20-28) and at ≥ 90 it was 12 (95% CI 7-22)). eGFR CysC also had the best accuracy in patients with reduced kidney function (P10 was 5.9% at 30-59 ml/min/1.73m²).

CONCLUSIONS

Cystatin C-based estimations of kidney function performed better than creatinine-based ones in patients with primary neuromuscular disease, but most importantly, all evaluated equations overestimated kidney function, especially in patients with reduced kidney function. Therefore, kidney function should be measured by gold-standard methods when precision and accuracy are needed.

Galectin-3-A New Player of Kidney Damage or an Innocent Bystander in Children with a Single Kidney?

The aim of this study was to evaluate the galectin-3 (Gal-3) level in children with a congenital solitary functioning kidney (cSFK) and determine its association with common renal function parameters. The study consisted of 68 children (49 males) with cSFK. We demonstrated that children with cSFK had a lower level of galectin-3 than that of healthy subjects (p < 0.001). No significant differences in serum cystatin C (Cys C) levels between the cSFK children and the reference group were found. The subjects with cSFK and reduced estimated glomerular filtration rate (eGFR) had significantly higher levels of Gal-3 and Cys C compared to those with normal eGFR (p < 0.05). Children with eGFR <60 mL/min/1.73 m² showed significant statistical differences between the values of area under ROC curve (AUC) for Gal-3 (AUC 0.91) and Cys C (AUC 0.96) compared to that for creatinine level (AUC 0.76). Similar analyses carried out among cSFK children with eGFR <90 mL/min/1.73 m² revealed an AUC value of 0.69 for Gal-3, 0.74 for Cys C, and 0.64 for creatinine; however, no significant superiority was shown for any of them. The receiver operating characteristic (ROC) analyses for identifying the SFK children among all participants based on the serum levels of Gal-3 and Cys C did not show any diagnostic profile (AUCs for Gal-3 and Cys C were 0.22 and 0.59, respectively). A positive correlation between the Gal-3 and Cys C concentrations was found (r = 0.39, p = 0.001). We demonstrated for the first time that Gal-3 might play an important role in the subtle kidney damage in children with cSFK. However, further prospective studies are required to confirm the potential applicability of Gal-3 as an early biomarker for kidney injury and possible progression to CKD.

Development and Evaluation of a Quantitative Fluorescent Lateral Flow Immunoassay for Cystatin-C, a Renal Dysfunction Biomarker

The diagnosis, prognosis, and control of chronic kidney disease rely on an understanding of the glomerular filtration rate (GFR). The renal clearance of the cystatin-C is closely associated with the GFR. Cystatin-C is a more suitable GFR marker than the commonly used creatinine. General techniques for cystatin-C calculation, such as particle-enhanced turbidimetric and nephelometric assay, are time-consuming and tedious. Here, we propose a rapid, quantitative immunoassay for the detection of cystatin-C. A fluorescence-based lateral-flow kit was developed in a sandwich format by using a monoclonal antibody. A Linear calibration was obtained over the clinical diagnostic range of 0.023-32 µg/mL and the limit of detection (LOD) was 0.023 µg/mL and the limit of quantification (LOQ) was 0.029 µg/mL. Average recoveries from spiked urine samples ranged from 96-100% and the coefficient of variation was less than 4% for both intra and inter-day assays with excellent repeatability. With the comparison with an ELISA kit, the developed kit is highly sensitive, performs well over the detection range, provides repeatable results in a short time, and can easily be used at point-of-care (POC), making it an ideal candidate for rapid testing in early detection, community screening for renal function disorders.

Acute kidney injury after lung transplantation: a narrative review

Acute kidney injury (AKI) is a commonly recognized complication after lung transplantation (LT) and is related to increased mortality and morbidity. With the improvement of survival after LT and the increasing number of lung transplant recipients, the detrimental impact of current management on renal function has become increasingly apparent. Multifarious risk factors in the perioperative setting contribute to the development of AKI, including the preoperative status and complications of the recipient, complex perioperative problems especially hemodynamic fluctuation, and exposure to nephrotoxic agents, mainly calcineurin inhibitors (CNIs) and antimicrobial drugs. Identification and minimization of the effects of these risk factors can relieve AKI severity and incidence in high-risk patients. Close monitoring of urine output and serum creatinine (sCr) levels and of specific biomarkers may promote early recognition of AKI and rapid nephrology intervention to improve outcomes. This review summarizes advances in the epidemiology, diagnostic criteria, biological markers of AKI, and further recommends appropriate treatment strategies for the long-term management of AKI related manifestations in lung transplant recipients. Future work will need to focus on developing more accurate measures of renal function and identifying patients before the occurrence of early renal damage. Combining renal protection strategies with the use of new biomarkers to develop early kidney risk identification and protection protocols is a promising idea that requires further investigation.

Early predictors of acute kidney injury in COVID-19 patients

Aim

This study aims to determine the frequency of COVID‐19 related AKI and to identify the early predictors of AKI.

Methods

This study is a single‐center, retrospective, observational study. Hospitalized COVID‐19 patients between 24/03/2020 and 31/05/2020 were included in the study. All patients were evaluated for renal dysfunctions with urine dipstick, protein/creatinine ratio, albumin/creatinine ratio in spot urine, serum cystatin C, serum creatinine level on hospital admission, and 28th day of hospital admission. To assess the utility of these parameters to predict AKI, a receiver‐operating characteristic curve was generated and the area under the curve (AUC) was calculated.

Results

348 patients were included. The average incidence of AKI was 4.9% (n = 17). The incidence of AKI in mild, moderate and severe COVID‐19 cases was 1.3% (n = 4), 9.0% (n = 3) and 76.9% (n = 10), respectively. Proteinuria was detected in 7.8% (n = 27) of patients with a urine dipstick test. In spot urine analysis, proteinuria was found in 20.1% (n = 70) of patients. The frequency of persistent proteinuria was 5.2% (n = 18). The AUC alue of serum cystatin C, D‐dimer and albumin/creatinine ratio to predict COVID‐19 related AKI were 0.96 (0.90 to 1.0), 0.94 (0.89–0.98), and 0.95 (0.91–0.98).

Conclusion

In COVID‐19 patients with normal serum creatinine levels on hospital admission, albuminuria, serum cystatin C and D‐dimer levels may be an early predictor of COVID‐19 related AKI and these patients should be monitored closely for AKI. Since the sample size in the AKI group was small, our study results should be confirmed with larger cohort studies.

This observational single‐center study assessed the frequency and predictors of acute kidney injury in 348 hospitalized patients with COVID‐19. In this cohort, AKI was diagnosed in 4.9% of patients and proteinuria (spot urine analysis) in 20%. Albuminuria/creatinine ratio, cystatin C‐ and D‐dimer were identified as potential predictors of AKI on admission.

Cystatin C, Vitamin D and Thyroid Function Test Profile in Chronic Kidney Disease Patients

BACKGROUND

The progression of chronic kidney disease (CKD) is concomitant with complications, including thyroid dysfunction, dyslipidemia and cardiovascular diseases. The aim of this study is to determine serum cystatin C levels, and the prevalence of vitamin D deficiency and thyroid dysfunction in CKD patients.

METHODS

A cross-sectional study was conducted involving 140 CKD patients (stages 1-5) that were referred to a renal clinic. Demographic data was collected and thyroid function tests, serum 25-OH-vitamin D, cystatin C levels, and routine biochemistry tests were determined using cobas 6000 analyzer.

RESULTS

129 (92.1%) of CKD patients had elevated serum cystatin C levels and there was a stepwise increase from stage 1-5. Overt hypothyroidism was present in one patient and nine had subclinical hypothyroidism. There was a stepwise reduction in serum 25-OH-vitamin D levels from stage 2-5, 31 (22.1%) had vitamin D insufficiency and 31 (22.1%) presented with deficiency.

CONCLUSIONS

25-OH-vitamin D deficiency and thyroid disorders are exhibited in chronic kidney disease patients and the severity of the former rises with disease progression, as indicated by elevated cystatin C levels. Routine screening and timely intervention is recommended so as to reduce the risk of cardiovascular diseases.

Serum NGAL, BNP, PTH, and albumin do not improve glomerular filtration rate estimating formulas in children

Glomerular filtration rate (GFR) is difficult to measure, and estimating formulas are notorious for lacking precision. This study aims to assess if the inclusion of additional biomarkers improves the performance of eGFR formulas. A hundred and sixteen children with renal diseases were enrolled. Data for age, weight, height, inulin clearance (iGFR), serum creatinine, cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), parathyroid hormone (PTH), albumin, and brain natriuretic peptide (BNP) were collected. These variables were added to the revised and combined (serum creatinine and cystatin C) Schwartz formulas, and the quadratic and combined quadratic formulas. We calculated the adjusted r-square (r²) in relation to iGFR and tested the improvement in variance explained by means of the likelihood ratio test. The combined Schwartz and the combined quadratic formulas yielded best results with an r² of 0.676 and 0.730, respectively. The addition of BNP and PTH to the combined Schwartz and quadratic formulas improved the variance slightly. NGAL and albumin failed to improve the prediction of GFR further. These study results also confirm that the addition of cystatin C improves the performance of estimating GFR formulas, in particular the Schwartz formula.Conclusion: The addition of serum NGAL, BNP, PTH, and albumin to the combined Schwartz and quadratic formulas for estimating GFR did not improve GFR prediction in our population. What is Known: • Estimating glomerular filtration rate (GFR) formulas include serum creatinine and/or cystatin C but lack precision when compared to measured GFR. • The serum concentrations of some biological parameters such as neutrophil gelatinase-associated lipocalin (NGAL), parathyroid hormone (PTH), albumin, and brain natriuretic peptide (BNP) vary with the level of renal function. What is New: • The addition of BNP and PTH to the combined quadratic formula improved its performance only slightly. NGAL and albumin failed to improve the prediction of GFR further.

Association Between the Concentration and Rangeability of Cystatin C and Mortality of COVID-19 Patients With or Without Type 2 Diabetes Mellitus: A Retrospective Analysis

BACKGROUND

We investigated if the concentration and "rangeability" of cystatin C (CysC) influenced the prognosis of coronavirus disease 2019 (COVID-19) in patients suffering from, or not suffering from, type 2 diabetes mellitus (T2DM).

METHODS

A total of 675 T2DM patients and 572 non-T2DM patients were divided into "low" and "high" CysC groups and low and high CysC-rangeability groups according to serum CysC level and range of change of CysC level, respectively. Demographic characteristics, clinical data, and laboratory results of the four groups were analyzed.

RESULTS

COVID-19 patients with a high level and rangeability of CysC had more organ damage and a higher risk of death compared with those with a low level or low rangeability of CysC. Patients with a higher level and rangeability of CysC had more blood lymphocytes and higher levels of C-reactive protein, alanine aminotransferase, and aspartate aminotransferase. After adjustment for possible confounders, multivariate analysis revealed that CysC >0.93 mg/dL was significantly associated with the risk of heart failure (OR = 2.231, 95% CI: 1.125-5.312) and all-cause death (2.694, 1.161-6.252). CysC rangeability >0 was significantly associated with all-cause death (OR = 4.217, 95% CI: 1.953-9.106). These associations were stronger in patients suffering from T2DM than in those not suffering from T2DM.

CONCLUSIONS

The level and rangeability of CysC may influence the prognosis of COVID-19. Special care and appropriate intervention should be undertaken in COVID-19 patients with an increased CysC level during hospitalization and follow-up, especially for those with T2DM.

Creatinine-Based Formulae Poorly Match in the Classification of Hypofiltration or Hyperfiltration in a General Population of Adolescents: A Retrospective Analysis of a Cross-Sectional Study

Pediatric formulae to estimate glomerular filtration rate (eGFR) give a broad range of values. Their consistency in assigning the subjects as hypofiltrating or hyperfiltrating is unknown. In 1993 apparently healthy adolescents (53.4% females) aged 14-17 years, we investigated the concordance of six creatinine-based formulae in the classification of the subjects into ≤ 5th or ≥95th percentile of eGFR, and the between-groups difference in the prevalence of cardiometabolic risk factors. Mean eGFR varied between 77 and 121 mL/min/1.73 m². Arbitrary setting of hypofiltration or hyperfiltration to 5% returned 46 males and 53 females. At least one formula classified 89 males and 99 females as hypofiltrating and 105 males and 114 females as hyperfiltrating. All six formulae concordantly classified 15 males and 17 females as hypofiltrating and 9 and 14, respectively, as hyperfiltrating. Pairwise, formulae consistently classified hypofiltration in 42-87% of subjects with hyperfiltration in 28-94%. According to two out of the six formulae, hyperfiltration was associated with an increased prevalence of obesity and obesity-associated comorbidities. Hypofiltrating subjects did not manifest chronic kidney disease-associated comorbidities. Further studies in different populations of healthy adolescents are needed before it is possible to conclude which creatinine-based formula is appropriate for the classification of hypofiltration and hyperfiltration in nonclinical cohorts.

Cystatin C is a potential predictor of unfavorable outcomes for cerebral ischemia with intravenous tissue plasminogen activator treatment: A multicenter prospective nested case-control study

BACKGROUND AND PURPOSE

The aim of this study was to explore whether cystatin C (CysC) could be used as a potential predictor of clinical outcomes in acute ischemic stroke (AIS) patients treated with intravenous tissue plasminogen activator (IV-tPA).

METHODS

We performed an observational study including a retrospective analysis of data from 125 AIS patients with intravenous thrombolysis. General linear models were applied to compare CysC levels between groups with different outcomes; logistic regression analysis and receiver-operating characteristic curves were adopted to identify the association between CysC and the therapeutic effects.

RESULTS

Compared with the "good and sustained benefit" (GSB) outcome group (defined as ≥4-point reduction in National Institutes of Health Stroke Scale or a score of 0-1 at 24 h and 7 days) and the "good functional outcome" (GFO) group (modified Rankin Scale score 0-2 at 90 days), serum CysC baseline levels were increased in the non-GSB and non-GFO groups. Logistic regression analysis found that CysC was an independent negative prognostic factor for GSB (odds ratio [OR] 0.010; p = 0.005) and GFO (OR 0.011; p = 0.021) after adjustment for potential influencing factors. Receiver-operating characteristic curves showed the CysC-involved combined models provided credible efficacy for predicting post-90-day favorable clinical outcome (area under the curve 0.86; p < 0.001).

CONCLUSIONS

Elevated serum CysC is independently associated with unfavorable clinical outcomes after IV-tPA therapy in AIS. Our findings provide new insights into discovering potential mediators for neuropathological process or treatment in stroke.

Effect of Cystatin C on Vancomycin Clearance Estimation in Critically Ill Children Using a Population Pharmacokinetic Modeling Approach

BACKGROUND

Vancomycin is eliminated by glomerular filtration, but current approaches to estimate kidney function in children are unreliable. The authors sought to compare the suitability of cystatin C (CysC)-based glomerular filtration rate equations with the most commonly used creatinine-based equation, bedside Schwartz, to estimate vancomycin clearance (CL).

METHODS

This prospective observational study enrolled critically ill patients (2-18 years) receiving intravenous vancomycin at the Children's Hospital of Philadelphia during December 2015-November 2017. Vancomycin levels were collected during clinical care and at 3 times during a single dosing interval. Plasma CysC was measured within 24 hours before intravenous vancomycin (baseline) initiation or immediately after enrollment and along with the third pharmacokinetic sample. Nonlinear mixed effects modeling was performed using NONMEM software. Covariate selection was used to test model fit with inclusion of the estimated glomerular filtration rate (eGFR) on CL using bedside Schwartz versus various published CysC-based equations.

RESULTS

In total, 83 vancomycin levels were obtained from 20 children. The median age was 12.7 years; 6 patients were women. A 1-compartment model best described the data; CL was allometrically scaled to 0.75. During covariate selection, inclusion of the eGFR calculated using a CysC-based equation significantly improved model fit [reduction in objective function value (OFV) range: -17.191 to -18.704] than bedside Schwartz ([INCREMENT]OFV -12.820). Including the full age spectrum equation, an eGFR equation based on both creatinine and CysC, led to the largest OFV reduction (-22.913); female sex was also a significant covariate of CL in the model. Final model pharmacokinetic indices were CL = 0.29 L/h/kg and volume of distribution = 0.48 L/kg.

CONCLUSIONS

CysC-based equations help better estimate vancomycin CL than bedside Schwartz in critically ill children.

A long journey for acute kidney injury biomarkers

Acute kidney injury (AKI) is a life-threatening illness that continues to have an in-hospital mortality rate of patients with AKI ranges from 20% to 50% or greater, depending on underlying conditions. However, it has only marginally declined over the past 25 years. Previous authoritative publications have been pointed out that the lack of useful biomarkers for AKI has limited progress in improving the outcomes of this disorder. The purpose of this paper is to review the recent biomarkers involved in the early detection of AKI and main reasons for the failure to identify new AKI biomarkers. So far, several new AKI biomarkers have been discovered and validated to improve early diagnosis, degree of severity, pathophysiology, differential diagnosis, prediction for major kidney adverse events (MAKE, risk groups for progressive renal failure, need for renal replacement therapy [RRT], or death). These biomarkers can be classified into functional, damage and pre-injury phase biomarkers. However, the clinical use of the studied biomarkers in AKI prediction remains unclear because large prospective multicenter trials have failed to demonstrate troponin-like diagnostic performance. Reasons for the failure to identify AKI biomarkers are the heterogeneity of AKI itself, biomarker limitations and long roads to the validation of candidates for new AKI biomarkers. In an effort to overcome these barriers to identifying new AKI biomarkers, kidney biopsy specimens should be obtained and assessed in human AKI populations. Research in this field should be carried out in a pan-social approach rather than conducted by just a few medical institutions.

Cystatin C and uncontrolled hypertension

Objective:

Increased serum level of cystatin C, a sensitive biomarker for renal function, seems to predict adverse cardiovascular events. We investigated the predictive value of serum cystatin C for controlling hypertension in an observational study.

Methods:

We screened 1037 adults residing in both rural and urban communities. They were grouped based on their diagnosis and control of hypertension.

Results:

Serum cystatin C levels in patients with uncontrolled hypertension were higher than those in patients with controlled hypertension (0.98±0.23 mg/L vs. 0.89±0.19 mg/L, p=0.001). However, serum creatinine levels were similar between these groups (0.72±0.20 mg/dL vs. 0.70±0.18 mg/dL, p=0.89). Serum cystatin C levels increased the probability of uncontrolled hypertension independent from confounding factors (odds ratio, 1.48; 95% confidence interval, 1.09–5.64; p=0.03).

Conclusion:

Subtle kidney dysfunction may be detected using serum cystatin C concentrations among patients with poor blood pressure control and normal serum creatinine levels.

Independent associations of urinary albumin-to-creatinine ratio and serum cystatin C with carotid intima-media thickness in community-living Taiwanese adults

Background

Renal function is a key factor of cardiovascular disease. Carotid intima-media thickness (IMT) has been widely used as a marker of early subclinical atherosclerosis. The determinants of cystatin C, a novel marker of renal function, have not been extensively studied in the Asian population. This study aimed to assess the determinants of cystatin C and explore whether carotid thickening was associated with urinary albumin-creatinine ratio and cystatin C in community-living Taiwanese adults.

Methods

A cross-sectional study was conducted on participants from Taichung City, Taiwan. All the participants underwent carotid ultrasonography. Carotid IMT-mean and IMT-maximum were derived. Kidney biomarkers were measured on the basis of urinary albumin-to-creatinine ratio (ACR) and cystatin C. Multiple linear regression analysis was used.

Results

A total of 1032 individuals were recruited, and 469 (45.44%) of them were men. An increased cystatin C level was significantly associated with older age, male gender, lack of physical activity, low HDL cholesterol, abdominal obesity, high hs-CRP, and high ACR. The multivariate-adjusted mean carotid IMT-mean and IMT-maximum values significantly increased by 80.49 and 195.23 μm for every one unit of increase in cystatin C level and by 0.07 and 0.14 μm for every one unit of increase in ACR, respectively (all p < 0.001 except ACR on IMT-maximum with p < 0.01). Lack of physical activity, low HDL, abdominal obesity, high hs-CRP, and high ACR were the determinants of cystatin C.

Conclusion

Cystatin C and ACR were strongly and linearly associated with carotid thickening, a marker of subclinical atherosclerosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-020-02123-x.

The validation of immunoblot SDS-PAGE as a qualitative and quantitative method for the determination of urinary Cystatin C in neonates

INTRODUCTION

The quantitative determination of urinary Cystatin C (cyst-C) associated with the qualitative analysis of its polymorphisms is an excellent method for early identification of newborns predisposed to renal function impairment. PETIA, PENIA and EIA are the immunometric methods used for the quantitative determination of cyst-C in human biologic fluid but they have limitations and do not allow qualitative analysis. The present study is a validation of Immunoblot SDS-PAGE for the qualitative and quantitative analysis of urinary cyst-C.

METHODS

Urine was collected from neonates in the nursey at S. Maria della Misericordia Hospital. Urinary cyst-C was investigated by the immunoblot SDS-PAGE and by reading of optical density.

RESULTS

The qualitative analysis showed two different molecular forms: a reactivity at about 70 KDa in all samples and a reactivity at 13 KDa in a limited number of samples. This analysis allows the correlation of the polymorphisms of cyst-C with specific alterations of renal function in newborns. The quantitative analysis is specific, sensitive and accurate. In fact the coefficient of variation for assay precision was 10% and for assay accuracy was ±10%, the detection limit was 0.009 ng/ µL and the calibration line has satisfactory linearity (range 0.02-0.3 ng/ µL). The stability of urinary cyst-C was acceptable, even without the use of protease inhibitors, as long as the assay was performed on freshly recruited urine or immediately after thawing the samples, which had been stored for up to six months.

CONCLUSION

Immunoblot SDS-PAGE analysis is a valid method of obtaining a qualitative and quantitative analysis of urinary cyst-C. This method presents unique information about a previously unknown 70 KDa cyst-C form. The assay may offer potential diagnostic information not available with immunometric method.

A Meta-Analysis on the Performance of Cystatin C- versus Creatinine-based eGFR Equations in Predicting Vancomycin Clearance

BACKGROUND

The objective of this study was to compare the performance of cystatin C- and creatinine-based estimated glomerular filtration rate (eGFR) equations in predicting the clearance of vancomycin.

METHODS

MEDLINE and Embase databases were searched from inception up to September 2019 to identify all studies that compared the predictive performance of cystatin C- and/or creatinine-based eGFR in predicting the clearance of vancomycin. The prediction errors (PEs) (the value of eGFR equations minus vancomycin clearance) were quantified for each equation and were pooled using a random-effects model. The root mean squared errors were also quantified to provide a metric for imprecision.

RESULTS

This meta-analysis included evaluations of seven different cystatin C- and creatinine-based eGFR equations in total from 26 studies and 1,234 patients. The mean PE (MPE) for cystatin C-based eGFR was 4.378 mL min^-1 (95% confidence interval [CI], -29.425, 38.181), while the creatinine-based eGFR provided an MPE of 27.617 mL min^-1 (95% CI, 8.675, 46.560) in predicting clearance of vancomycin. This indicates the presence of unbiased results in vancomycin clearance prediction by the cystatin C-based eGFR equations. Meanwhile, creatinine-based eGFR equations demonstrated a statistically significant positive bias in vancomycin clearance prediction.

CONCLUSION

Cystatin C-based eGFR equations are better than creatinine-based eGFR equations in predicting the clearance of vancomycin. This suggests that utilising cystatin C-based eGFR equations could result in better accuracy and precision to predict vancomycin pharmacokinetic parameters.

Initial Dosage Optimization of Tacrolimus in Pediatric Patients With Thalassemia Major Undergoing Hematopoietic Stem Cell Transplantation Based on Population Pharmacokinetics

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is an effective treatment for hematological disorders. Tacrolimus is widely used after HSCT, but it has highly interindividual variable pharmacokinetics. Population pharmacokinetics (PPK) researches of tacrolimus in children with β-thalassemia major (β-TM) undergoing HSCT are insufficient.

OBJECTIVE

To establish a PPK model of tacrolimus in children with β-TM and optimize initial dosing regimen for achieving target concentration of 5 to 15 ng/mL.

METHODS

Data on patients aged <18 years were retrospectively collected from January 2017 to December 2018. PPK analysis and Monte Carlo simulations were performed using nonlinear mixed-effects modeling.

RESULTS

A data set of 55 patients with 332 concentrations was included. A 2-compartment model could best describe the pharmacokinetics of tacrolimus. The body surface area and gender were significant covariates in the final model. The typical value of clearance, the distribution volume of the central room, the distribution volume of the peripheral room, and the intercompartmental clearance were 5.05L/h, 4.33L, 155L, and 6.22L/h, respectively. The optimal initial dosing regimen of 0.03, 0.04, 0.05, 0.06, and 0.10 mg/kg were appropriate for female children with a weight (WT) of 50 to 10 kg. The regimen of 0.04, 0.05, 0.06, 0.07, and 0.12 mg/kg is suitable for male children with a WT of 50 to 10 kg. The probability of target attainment (PTA) of each regimen reached 91%.

CONCLUSION AND RELEVANCE

A stable PPK model of tacrolimus was established. The proposed dosage regimen reached a good PTA, which could provide a reference for tacrolimus therapy.

Urinary Cyclophilin A and serum Cystatin C as biomarkers for diabetic nephropathy in children with type 1 diabetes

BACKGROUND

Currently, microalbuminuria is the gold standard for detection and prediction of diabetic nephropathy (DN). However, microalbuminuria appears once significant kidney damage has actually occurred.

OBJECTIVES

We investigated the diagnostic role of urinary Cyclophilin-A (uCypA), uCypA/creatinine ratio (uCypA/Cr) and serum Cystatin-C (sCysC) as biomarkers for early detection of DN in children with type 1 diabetes mellitus (T1DM) of short duration (2-5 years) before microalbuminuria emerges.

METHODS

uCypA, uCypA/Cr, and sCysC levels were assessed in three age- and sex-matched groups; microalbuminuric diabetic group (n = 31), normoalbuminuric diabetic group (n = 29), and control group (n = 30). Glomerular filtration rate was estimated (eGFR) based on both serum creatinine (eGFR-Cr) and sCysC (eGFR-CysC).

RESULTS

Significantly higher sCysC and lower eGFR-CysC were detected in both diabetic groups compared to controls and in microalbuminuric compared to normoalbuminuric group. No detected significant difference in eGFR-Cr values across the studied groups. Both uCypA and uCypA/Cr were significantly elevated in microalbuminuric compared to both normoalbuminuric and control groups with no difference between normoalbuminuric and control groups. Prediction of microalbuminuria was conducted using sCysC with area under curve up to 0.980. Combined use of sCysC and uCypA had better diagnostic value than uCypA alone.

CONCLUSION

sCysC is a promising early biomarker for DN in childhood T1DM before albuminuria detection. eGFR-CysC is superior to eGFR-Cr in evaluating renal status in childhood T1DM. uCypA and uCypA/Cr were useful tools in predicting microalbuminuria, although not regarded as diagnostic biomarkers for early-stage DN in T1DM children by the current study.

Longitudinal proteomics analysis in the immediate microenvironment of islet allografts during progression of rejection

The applicability and benefits of pancreatic islet transplantation are limited due to various issues including the need to avoid immune-mediated rejection. Here, we used our experimental platform of allogeneic islet transplant in the anterior chamber of the eye (ACE-platform) to longitudinally monitor the progress of rejection in mice and obtain aqueous humor samples representative of the microenvironment of the graft for accurately-timed proteomic analyses. LC-MS/MS-based proteomics performed on such mass-limited samples (~5 μL) identified a total of 1296 proteins. Various analyses revealed distinct protein patterns associated with the mounting of the inflammatory and immune responses and their evolution with the progression of the rejection. Pathway analyses indicated predominant changes in cytotoxic functions, cell movement, and innate and adaptive immune responses. Network prediction analyses revealed transition from humoral to cellular immune response and exacerbation of pro-inflammatory signaling. One of the proteins identified by this localized proteomics as a candidate biomarker of islet rejection, Cystatin 3, was further validated by ELISA in the aqueous humor. This study provides (1) experimental evidence demonstrating the feasibility of longitudinal localized proteomics using small aqueous humor samples and (2) proof-of-concept for the discovery of biomarkers of impending immune attack from the immediate local microenvironment of ACE-transplanted islets. SIGNIFICANCE: The combination of the ACE-platform and longitudinal localized proteomics offers a powerful approach to biomarker discovery during the various stages of immune reactions mounted against transplanted tissues including pancreatic islets. It also supports proteomics-assisted drug discovery and development efforts aimed at preventing rejection through efficacy assessment of new agents by noninvasive and longitudinal graft monitoring.

NOX4 Deficiency Exacerbates the Impairment of Cystatin C-Dependent Hippocampal Neurogenesis by a Chronic High Fat Diet

Hippocampal neurogenesis is linked with a cognitive process under a normal physiological condition including learning, memory, pattern separation, and cognitive flexibility. Hippocampal neurogenesis is altered by multiple factors such as the systemic metabolic changes. NADPH oxidase 4 (NOX4) has been implicated in the regulation of brain function. While the role of NOX4 plays in the brain, the mechanism by which NOX4 regulates hippocampal neurogenesis under metabolic stress is unclear. In this case, we show that NOX4 deficiency exacerbates the impairment of hippocampal neurogenesis by inhibiting neuronal maturation by a chronic high fat diet (HFD). NOX4 deficiency resulted in less hippocampal neurogenesis by decreasing doublecortin (DCX)-positive neuroblasts, a neuronal differentiation marker, and their branched-dendrites. Notably, NOX4 deficiency exacerbates the impairment of hippocampal neurogenesis by chronic HFD. Moreover, NOX4 deficiency had a significant reduction of Cystatin C levels, which is critical for hippocampal neurogenesis, under chronic HFD as well as normal chow (NC) diet. Furthermore, the reduction of Cystatin C levels was correlated with the impairment of hippocampal neurogenesis in NOX4 deficient and wild-type (WT) mice under chronic HFD. Our results suggest that NOX4 regulates the impairment of Cystatin C-dependent hippocampal neurogenesis under chronic HFD.

Prognostic Value of Cystatin C-Derived Estimated Glomerular Filtration Rate in Patients with Acute Heart Failure

Background: Renal function is closely related to cardiac function and an important prognostic marker in heart failure. Objective: We aimed to test the prognostic value of cystatin C (cysC)-derived estimated glomerular filtration rates (eGFR) in comparison with eGFRs from creatinine solely based equations in patients with acute heart failure (AHF). Methods: This study included 262 patients (65.8 ± 14.9 years old, 126 male) with AHF. Prognostic value of the eGFRs, from cysC-based equations chronic kidney disease epidemiology collaboration (CKD-EPI-cysC and CKD-EPI-creatinine [cr]-cysC equations) were compared with eGFRs calculated from serum creatinine levels only (Modification of Diet in Renal Disease [MDRD]-4 and CKD-EPI-cr equations). Prognosis was evaluated with the composite of all-cause mortality and hospitalization for heart failure within 1 year. Results: During the follow-up period (mean follow-up period, 264.0 ± 136.1 days), 67 (25.6%) events occurred. Estimated GFR using CKD-EPI-cysC was the best for predicting 1-year outcome using receiver operating characteristic curve analysis (area under curve 0.585, 0.607, 0.669, and 0.652 for eGFRs from MDRD-4, CKD-EPI-cr, CKD-EPI-cysC, and CKD-EPI-cr-cysC respectively). The Kaplan-Meier survival curve analysis showed that only the eGFRs classification from the equations based on cysC significantly predicted 1-year outcome in patients with AHF. Conclusions: Estimated GFRs calculated with cysC predicted the prognosis more accurately in patients with AHF than the eGFRs from creatinine only equations.

GFR Measurement and Chemotherapy Dosing in Patients with Kidney Disease and Cancer

Chemotherapeutic agents require precise dosing to ensure optimal efficacy and minimize complications. For those agents that are removed from the body by the kidney, accurate knowledge of GFR is critical. In addition, GFR needs to be determined rapidly, easily, and, if possible, with little additional cost. The ability to easily measure GFR also allows for rapid detection of nephrotoxicity. Current methodologies include direct clearance measurement of an indicator substance or estimation of creatinine clearance or GFR through regression equations that use a serum marker, such as creatinine or cystatin C. These methodologies all have shortfalls and limitations, some of which are specific to the patient with cancer. Newer methodologies that directly measure GFR are in clinical trials and offer the ability to rapidly and noninvasively provide accurate estimates of drug clearance as well as detection of nephrotoxicity. These methods offer the opportunity to refine drug dosing and improve outcomes.

Kidney function in minority children and adolescents with metabolically healthy and unhealthy obesity

Metabolic syndrome and/or body mass index (BMI) ≥40 kg/m² are risk factors for kidney function decline in the general population. To compare creatinine (Cr), estimated glomerular filtration rate (eGFR) and blood urea nitrogen (BUN) between minority children and adolescents with metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO), a chart review was conducted on subjects aged 4 to 20 years with BMI ≥95^th percentile from July 2014 to April 2017. They were stratified into MHO and MUO groups. Cr, eGFR and BUN were studied. Total n = 277: MHO n = 105 vs MUO n = 172. Cr was higher and BUN was lower in MUO whereas eGFR did not differ between the groups. Using general linear model, we found that metabolic status predicted BUN (P = .009) but not Cr or eGFR. When age, sex and Tanner stage matched, BUN, Cr and eGFR were similar between the groups. Higher BUN in MHO could be due to higher dietary protein intake. Subjects were divided into BMI ≥40 vs <40 kg/m² , BUN and eGFR were not different. A trend towards higher Cr in those with BMI ≥40 kg/m² (P = .054) was found; the group being older and taller. After age and height matching, all outcomes were not different. Higher Cr was found in those with elevated blood pressures vs the MHO (P = .047). Those with diastolic blood pressure (DBP) ≥90^th percentile had higher Cr than those with systolic blood pressure ≥90^th percentile (P = .017). Children and adolescents with MUO, and those with BMI ≥40 kg/m² did not appear to have early diminished kidney function. Higher Cr, although in normal range, occurred in those with abnormal DBP.