Comparison of cystatin C, creatinine and creatinine clearance vs. GFR for detection of renal failure in renal transplant patients

Background: Serum cystatin C (Scyst) has been suggested as an alternative index of glomerular filtration rate (GFR) and could be useful in renal transplant patients. Methods: In a 60-subject cohort (40+/-12 years old), we compared the simultaneous measurements of Scyst, serum creatinine (Screat), creatinine clearance (Ccreat), Cockcroft and Gault's estimated clearance (Ccg) and GFR measured using inulin clearance (Cin). Receiver operating characteristic (ROC) analysis was performed using two Cin cut-off (60 and 90 mL/min/1.73 m(2)). Results: A significant correlation was found among Cin on one hand and 1/Scyst, Ccreat, 1/Screat and Ccg on the other hand. Best fits (sensitivity/specificity) at 90 mL/min/1.73 m(2) were 1.18 mg/L (0.72/0.80) for Scyst, 1.32 mg/dL (0.67/0.90) for Screat, 77 mL/min (0.80/0.70) for Ccg and 104 mL/min (0.88/0.80) for Ccreat. The areas under the ROC curves were not significantly different. Conclusions: This study provides cut-off values for Screat and Cc for detection of renal failure in renal transplant patients. However, the results also suggest that Scyst is not a more sensitive marker than Screat or Ccg for detecting renal failure in renal transplant patients.