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. J. Clin. Lab. Anal. 18:61–64, 2004. © 2004 Wiley‐Liss, Inc.
Keywords: cystatin C, creatinine clearance, glomerular filtration rate, ROC curve
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