Correlation of Serum Concentrations of Cystatin C and Creatinine to Inulin Clearance in Liver Cirrhosis

The gold standard for the evaluation of the glomerular filtration rate (GFR) is inulin clearance (CIn), but its widespread use is prevented by several technical difficulties (1). The most commonly used marker for GFR is serum creatinine. However, serum creatinine concentrations should be interpreted with caution as a filtration marker in liver cirrhosis because they do not adequately reflect renal dysfunction. Increased tubular secretion and muscle wasting account for the disparity between creatinine concentrations and GFR in cirrhotic patients (2)(3)(4). Thus, GFR has been demonstrated repeatedly to be overestimated by serum creatinine (1)(2)(3)(4)(5). Cystatin C, a cationic 13-kDa protein that is produced by nucleated cells and catabolized by the renal tubular cells after passing the glomerular filter, has recently been reported as a reliable endogenous marker of GFR in healthy adults and children as well as in patients with nephrologic, urologic, and rheumatologic disorders (6)(7)(8)(9). For patients with liver cirrhosis, however, no data are available. Therefore, we studied cystatin C in comparison to creatinine for the assessment of GFR in these patients. We also determined the precision (10) of each analyte to predict GFR in cirrhotic patients.