Clinical Value of Serum Cystatin C by ELISA for Estimation of Glomerular Filtration Rate

Abstract

The search for whether endogenous markers of changes in glomerular filtration rate (GFR) by serum cystatin C assay and serum cystatin C compare with creatinine clearance by the Cockeroft-Gault formula and the evaluation of its clinical significance as a marker of GFR is important in clinical practice at present. Serum cystatin C was determined by sandwich enzyme immunoassay using a kit. Control blood samples were collected from 70 healthy subjects and 168 patients with various kidney diseases. Creatinine clearance (Cockeroft-Gault formula) as a measure of GFR, in 168 patients with various kidney diseases, depends on the creatinine clearance; GFR parameters were used to divide patients into two groups. The GFR was > 80 mL/min in 38 patients (group A) and < 80 mL/min in 130 patients (group B). The two groups were analyzed by correlation coefficient and diagnostic sensitivity and specificity were assessed by the receiver-operating characteristic (ROC) plots (area under the curve). Of the 70 healthy control individuals, the serum level of cystatin C was measured as normal value range and a reference interval of 1.05 ± 0.18 μg/mL (mean ± 1.96 SD, 95% confidence limits for the upper references limit is 1.4 μg/mL). In group A, serum cystatin C had no correlation to the creatinine clearance (r = 0.171, P > 0.05) and in group B, serum cystatin C was closely correlated to the creatinine clearance (r = -0.771, P < 0.001). Diagnostic sensitivity and specificity were assessed by the ROC plots for serum cystatin C (area under the curve = 0.8461, SE = 0.057) and creatinine clearance (area under the curve = 0.7642, SE = 0.068). These data suggest that combined measurement of serum cystatin C is useful to estimate GFR, especially to detect the reduction of GFR. Further studies are required to evaluate the whether serum cystatin C as a more sensitive marker of early renal injury might be extremely useful, particularly in nonproteinuric or unapparent renal disease. © 2004 Wiley-Liss, Inc.