Cystatin C-based calculation of glomerular filtration rate in kidney transplant recipients

Abstract

Cystatin C (Cys C) has been shown to be an alternative marker of renal function. However, estimation of the glomerular filtration rate (GFR) based on Cys C has received little attention. Recently, several Cys C-based equations were developed in different patient cohorts. To date, the benefit of a Cys C-based GFR calculation in patients after renal transplantation (RTx) remains to be elucidated. We compared the diagnostic accuracy of three Cys C-based formulae (Larsson, Hoek, Filler which used an immunonephelometric method) with the results of the Modification of Diet in Renal Disease (MDRD) formula. GFR was measured by means of technetium-diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) clearance in 108 consecutive patients after RTx. Correlation coefficients of all calculated GFR estimates with the true GFR were high but did not differ significantly from one another (0.83-0.87). The MDRD and Filler equations overestimated GFR significantly, whereas the Larsson equation significantly underestimated GFR. Bias of the Hoek formula was negligible. Precision of the Hoek (8.9 ml/min/1.73 m(2)) and Larsson equations (9.6 ml/min/1.73 m(2)) were significantly better than MDRD equations (11.4 ml/min/1.73 m(2); P< or =0.035 each). Accuracy within 30% of real GFR was 67.0 and 65.1% for the MDRD and Filler formulae, and 77.1% for the Larsson and Hoek formulae, respectively. Accuracy within 50% of true GFR for the Hoek formula (97.2%) was better than for the MDRD equations (85.3%). Cys C-based formulae may provide a better diagnostic performance than creatinine-based equations in GFR calculation after RTx.

The Impact of Interlaboratory Differences in Cystatin C Assay Measurement on Glomerular Filtration Rate Estimation

“…Twenty percent of patients with stage 3 CKD using Mayo Clinic values had an eGFR greater than 60 ml/min per 1.73 m 2 using CHEO values. These results support the suggestion that interlaboratory differences contribute to some of the heterogeneity in equation performance observed in validation studies using Siemens' PENIA assay (13)(14)(15)(16).…”

“…Differences between PENIA, PETIA, and ELISA methodologies have been explored by a number of groups, with notable differences demonstrated (5,6). However, these studies do not address the variability in equation performance seen in studies that utilized the same methodology and manufacturer (13)(14)(15)(16). The purpose of this study was to examine the differences in CysC measured using Siemens' PENIA assay in two different laboratories experienced in measuring CysC and the effect any differences would have on GFR estimation.…”

Accuracy of Different Equations in Estimating GFR in Pediatric Kidney Transplant Recipients

“…Plasma cystatin C (CystC), an endogenous lowmolecular-weight protein, overcomes PCr limitations (2,(5)(6)(7)(8). CystC meets only a few criteria of an ideal renal function marker because it is produced at a constant rate and is freely filtered in the glomerulus without tubular secretion; however, it is catabolized in the tubulus (9).…”

A New Approach for Evaluating Renal Function and Its Practical Application

“…Formulas using the serum cystatin C concentration to estimate GFR Some formulas using the serum cystatin C concentration based on the particle-enhanced immunonephelometric assay (PENIA) or immunoturbidimetric assay (PETIA) in order to estimate GFR have recently been reported (Table 1) (14 -19). The diagnostic accuracy of three cystatin C-based formulas (Larson, Hoek, and Filler formulae) that used an immunonephelometric method was evaluated in liver transplant recipients (20) and in kidney transplant recipients (21). In both reports, the Hoek formula showed the best overall performance for GFR with respect to bias, precision, and accuracy.…”