Diagnostic Accuracy of Cystatin C–Based eGFR Equations at Different GFR Levels in Children

Abstract

SummaryBackground and objectives The diagnostic accuracy of cystatin C estimated GFR (eGFR) by various cystatin C equations have varied in different studies. We hypothesized that the GFR level of enrolled patients affects the diagnostic accuracy of a cystatin C equation.Design, setting, participants, & measurements We analyzed 240 consecutively enrolled children at a single Canadian center in a prospective and cross-sectional study. Cystatin C was analyzed with nephelometry, and cystatin C eGFR was estimated by the equations validated in children. GFR was measured by technetium-99m-diethylene-triamine penta-acetic acid ( 99m Tc DTPA).Results We compared various cystatin C equations across GFR strata Ͻ60, Ͻ90, Ն135, and Ն150 ml/min per 1.73 m 2 for an accurate prediction and appropriate classification of the measured GFR. The CKiD, Zappitelli-CysEq, and Zappitelli-CysCrEq equations had a higher accuracy, estimated by eGFR values within 10% and 30% of the respective 99m Tc DTPA, in the GFR categories Ͻ60 and Ͻ90 ml/min per 1.73 m 2 , whereas the Bö kenkamp, Bouvet, and Filler equations had a greater accuracy in the GFR categories Ն135 and Ն150 ml/min per 1.73 m 2 . The Bouvet, CKiD, Filler, Zappitelli-CysEq, and Zappitelli-CysCrEq equations had a greater sensitivity to classify GFR Ͻ60 and Ͻ90 ml/min per 1.73 m 2 , whereas the Bö kenkamp equation had a higher sensitivity for GFR Ն135 and Ն150 ml/min per 1.73 m 2 . ConclusionsThe diagnostic accuracy of various cystatin C equations varies with GFR. This issue needs consideration while applying these equations in clinical practice and for further research on eGFR equations.

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

“…Similar results were obtained by the pilot study conducted by Krieser et al (26) found considerable heterogeneity in the performance of CystC-based equations. In addition, by analyzing data on 240 children, Sharma et al (27) found that the diagnostic accuracy of various CystC-based equations varied with mGFR. Some equations performed better at low mGFR levels and others at high mGFR levels.…”

Modification of the Schwartz equations for children increases their accuracy at eGFR > 60 mL/min/1.73 m2

“…A detailed analysis of Tables 17 and 18 The Filler equation has been found to significantly overestimate the value of real GFR by the mean percentage of 7.8-39%, what has been pointed out. 29,37,38 The bi-marker equation of Zappitelli shows a slight mean error of 18.5% and its accuracy mildly decreases only at high values of GFR >135 mL/min/1.73 m 2 . Importantly at GFR >135 mL/min/1.73 m 2 , none of the equations, with the exception of the modified trimarker Schwartz formula (GFR S3M C), shows a significant correlation with the reference method.…”

“…29,34 This is why the relative error (RE) expressed as a percentage value was chosen as the basic method of comparing to GFR I and to values originating from the analyzed equation:…”

“…20,24,25 The 2009 shortened equation of Schwartz has been evaluated in children with high GFR values, 1,4,12,[26][27][28] but only isolated papers estimated the accuracy of the tri-marker equation. 29 Chehade et al…”

New Combined Serum Creatinine and Cystatin C Quadratic Formula for GFR Assessment in Children

“…We found that the best-fit model of correlation between iGFR and CysC is linear, but it is still far below the KDOQI targets to be validated, with ,90% of estimated GFRs reaching 30% accuracy (21). Regarding the solely SCreat-based formulas for eGFR, the linear model proposed by Schwartz et al is inaccurate SCreat, serum creatinine; CysC, cystatin C. (24). All these findings have important implications for public health and clinical practice, particularly in conditions of less renal impairment or normal GFR.…”