Plasma cystatin C as a marker of renal function in patients with liver cirrhosis.

Cystatin C is a low molecular weight protein and the plasma level of cystatin C is mainly determined by glomerular filtration, making cystatin C an endogenous marker of glomerular filtration rate. The aim of the study was to elucidate the applicability of plasma cystatin C as a marker of renal function in patients with liver cirrhosis. Serum cystatin C and creatinine concentrations were compared with creatinine clearance. Thirty-six patients (14 females and 22 males aged between 33 and 81 years) with liver cirrhosis with normal to severely impaired kidney function were included. Plasma cystatin C was measured by an automated particle-enhanced nephelometric immunoassay (Dade Behring Diagnostics) and plasma creatinine by an enzymatic method. Plasma levels of cystatin C and creatinine were found to increase with decreasing values of creatinine clearance. The reciprocal values of cystatin C and creatinine were compared with those for creatinine clearance revealing an r2 of 0.37 and 0.18, respectively. Comparison of the areas under the curves (AUC) of the non-parametric receiver-operating characteristic plots for plasma cystatin C (AUC=0.7364; SE=0.0929) and plasma creatinine (AUC=0.6309: SF=0.1028) revealed a significant difference between plasma cystatin C and plasma levels of creatinine (p-value=0.03). The results demonstrate that the diagnostic accuracy of plasma cystatin C was better than plasma creatinine in identifying liver cirrhotic patients with reduced glomerular filtration rate.