Glomerular filtration rate assessment in individuals after orthotopic liver transplantation based on serum cystatin C levels.

Individuals after orthotopic liver transplantation (OLT) often show renal dysfunction, which may substantially affect the post-OLT course. Renal function after OLT is commonly assessed by means of serum creatinine (S(cr)) concentration or renal creatinine clearance (C(cr)). A glomerular filtration rate (GFR) estimate based on S(cr) level is not accurate enough because even a more marked decrease in GFR need not be associated with an increase in S(cr) level, especially in jaundiced patients. The study intends to try to estimate GFR in individuals after OLT by means of determining serum cystatin C (S(cyst)) concentrations. In 58 individuals (mean age, 49 +/- 7 years; 31 men, 27 women) at various intervals from OLT (mean, 14 +/- 10 months), GFR was estimated by using simultaneous determinations of S(cyst), S(cr), C(cr), and renal inulin clearance (C(in)). In most subjects (91.3%), C(in) was decreased to less than the lower limit of normal (80 mL/min/1.73 m(2)). A significant correlation (r = 0.70; P <.001) was found between 1/S(cyst) and C(in). Receiver operating characteristic analysis was performed on S(cyst) and S(cr) using a C(in) cutoff value of 80 mL/min/1.73 m(2). The area under the curve for S(cyst) was 0.912 +/- 0.044, and that for S(cr), 0.899 +/- 0.049. There was no statistically significant difference between these values. The sensitivity for a S(cyst) level of 1.20 mg/L (upper limit of normal value) to detect a decrease in GFR (measured as C(in)) below the lower limit of normal (80 mL/min/1.73 m(2)) was 96.1%. The sensitivity of S(cyst) level was significantly greater (P <.01) than the sensitivity of S(cr) level for men and at borderline significance for women (P =.05). Findings support the assumption that a S(cyst) level less than 1.2 mg/L indicates with a high degree of probability (P <.001) that GFR is not decreased to less than the normal limit. S(cyst) assessment in individuals after OLT could be proposed as a confirmatory test of a decrease in GFR in individuals with normal S(cr) levels.