Comparison of cystatin C, creatinine, and iohexol clearance in pediatric liver transplantation-a retrospective cohort study

Comparison of estimated GFR using cystatin C versus creatinine in pediatric kidney transplant recipients

BACKGROUND

An accurate, rapid estimate of glomerular filtration rate (GFR) in kidney transplant patients affords early detection of transplant deterioration and timely intervention. This study compared the performance of serum creatinine (Cr) and cystatin C (CysC)-based GFR equations to measured GFR (mGFR) using iohexol among pediatric kidney transplant recipients.

METHODS

CysC, Cr, and mGFR were obtained from 45 kidney transplant patients, 1-18 years old. Cr- and CysC-estimated GFR (eGFR) was compared against mGFR using the Cr-based (Bedside Schwartz, U25-Cr), CysC-based (Gentian CysC, CAPA, U25-CysC), and Cr-CysC combination (CKiD Cr-CysC, U25 Cr-CysC) equations in terms of bias, precision, and accuracy. Bland-Altman plots assessed the agreement between eGFR and mGFR. Secondary analyses evaluated the formulas in patients with biopsy-proven histological changes, and K/DOQI CKD staging.

RESULTS

Bias was small with Gentian CysC (0.1 ml/min/1.73 m2); 88.9% and 37.8% of U25-CysC estimations were within 30% and 10% of mGFR, respectively. In subjects with histological changes on biopsy, Gentian CysC had a small bias and U25-CysC were more accurate-both with 83.3% of and 41.7% of estimates within 30% and 10% mGFR, respectively. Precision was better with U25-CysC, CKiD Cr-CysC, and U25 Cr-CysC. Bland-Altman plots showed the Bedside Schwartz, Gentian CysC, CAPA, and U25-CysC tend to overestimate GFR when > 100 ml/min/1.72 m2. CAPA misclassified CKD stage the least (whole cohort 24.4%, histological changes on biopsy 33.3%).

CONCLUSIONS

In this small cohort, CysC-based equations with or without Cr may have better bias, precision, and accuracy in predicting GFR.

Cystatin C as a GFR Estimation Marker in Acute and Chronic Illness: A Systematic Review

Rationale & Objective

Creatinine-based GFR estimating (eGFRcr) equations may be inaccurate in populations with acute or chronic illness. The accuracy of GFR equations that use cystatin C (eGFRcys) or creatinine-cystatin C (eGFRcr-cys) is not well studied in these populations.

Study Design

A systematic review of original articles identified from PubMed and expert sources. Two reviewers screened articles independently and identified those meeting inclusion criteria.

Setting & Study Populations

Adults and children with acute or chronic illness.

Selection Criteria for Studies

Studies published since 2011 that compared performance of eGFRcr, eGFRcys, and eGFRcr-cys relative to measured GFR (mGFR), used standardized assays for creatinine or cystatin C, and used eGFR equations developed using such assays. Studies of ambulatory clinical populations or research studies in populations with only CKD, kidney transplant recipients, only diabetes, kidney donor candidates, and community-based cohorts were excluded.

Data Extraction

Data extracted from full text.

Analytical Approach

Bias and percentages of estimates within 30% of mGFR (P30) of eGFR compared with mGFR were evaluated.

Results

Of the 179 citations, 26 studies met the inclusion criteria: 24 in adults and 2 in children in clinical populations with cancer (n=5), HIV (n=5), cirrhosis (n=3), liver transplant (n=3), heart failure (n=2), neuromuscular diseases (n=1) critical illness (n=5), and obesity (n=2). In general, eGFRcr-cys had greater accuracy than eGFRcr or eGFRcys equations among study populations with cancer, HIV, and obesity, but did not perform consistently better in cirrhosis, liver transplant, heart failure, neuromuscular disease, and critical illness.

Limitations

Participants were selected because of concern for inaccurate eGFRcr, which may bias results. Most studies had small sample sizes, limiting generalizability.

Conclusions

eGFRcr-cys improves GFR estimation in populations with a variety of acute and chronic illnesses, providing indications for cystatin C measurement. Performance was poor in many studies, suggesting the need for more frequent mGFR.

Plain-Language Summary

Kidney function, specifically glomerular filtration rate (GFR), estimated using creatinine (eGFRcr) is often inaccurate in people with acute and chronic illness. The accuracy of estimates using cystatin C alone (eGFRcys) or together with creatinine (eGFRcr-cys) is not well studied in these populations. We conducted a systematic review to address the knowledge gap. Of the 179 papers reviewed, we identified 26 studies in clinical populations with cancer (n=5); HIV (n=5); cirrhosis (n=3); liver transplant (n=3); heart failure (n=2); neuromuscular disease (n=1); critical illness (n=5); and obesity (n=2). In general, eGFRcr-cys improved the GFR estimation in HIV, cancer, and obesity, providing indications for cystatin C measurement. Performance was poor in many studies, suggesting the need for more frequent measured GFR.

Kidney injury associated with liver transplantation

INTRODUCTION

Kidney injury associated with paediatric liver transplantation (LT) is common, but its evaluation is challenging. Our aim was to analyse the presence of perioperative acute kidney injury (AKI) and study the prevalence of chronic kidney disease (CKD) using different glomerular filtration rate (GFR) estimation formulas.

METHODS

We conducted a cross-sectional study in a cohort of children aged less than 18 years with a history of LT followed up for 5.42 years. We estimated the GFR using the creatinine-based Schwartz bedside formula (2009), the cystatin C-based Caucasian Asian Pediatric and Adult cohort (CAPA) equation and the combined Full-Age Spectrum (FAS) formula as modified by Pottel. We analysed the agreement between them using the Bland-Altman method and the kappa statistic. We measured the albumin level in urine, the urine volume adjusted to 100 mL of GFR and blood pressure. We performed univariate and multivariate analyses of the risk factors associated with CKD.

RESULTS

The sample included 52 patients with a median age of 9.21 years. Fifteen (28.8%) had AKI. Five (10%) had CKD and the only associated risk factor was acute liver failure at the time of LT (odds ratio, 8.57; P = 0.04). There was poor agreement between the different estimation formulas. One patient was classified as having CKD with the Schwartz formula compared to four patients with the CAPA and the Pottel combined FAS formulas. Up to 42% of children without CKD had some positive marker of kidney injury.

CONCLUSIONS

The exclusive use of the 2009 Schwartz bedside formula to estimate GFR may lead to underdiagnosis of CKD in children post LT. Other markers of kidney injury are common, and their detection may help prevent the progression of CKD.

PCRRT Expert Committee ICONIC Position Paper on Prescribing Kidney Replacement Therapy in Critically Sick Children With Acute Liver Failure

Management of acute liver failure (ALF) and acute on chronic liver failure (ACLF) in the pediatric population can be challenging. Kidney manifestations of liver failure, such as hepatorenal syndrome (HRS) and acute kidney injury (AKI), are increasingly prevalent and may portend a poor prognosis. The overall incidence of AKI in children with ALF has not been well-established, partially due to the difficulty of precisely estimating kidney function in these patients. The true incidence of AKI in pediatric patients may still be underestimated due to decreased creatinine production in patients with advanced liver dysfunction and those with critical conditions including shock and cardiovascular compromise with poor kidney perfusion. Current treatment for kidney dysfunction secondary to liver failure include conservative management, intravenous fluids, and kidney replacement therapy (KRT). Despite the paucity of evidence-based recommendations concerning the application of KRT in children with kidney dysfunction in the setting of ALF, expert clinical opinions have been evaluated regarding the optimal modalities and timing of KRT, dialysis/replacement solutions, blood and dialysate flow rates and dialysis dose, and anticoagulation methods.