The inaccuracy of cystatin C and creatinine-based equations in predicting GFR in orthotopic liver transplant recipients

Methods. This was a cross-sectional study performed on OLT recipients within a single liver transplant centre where creatinine (n = 41) and cystatin C (n = 30) were measured and glomerular filtration rate (GFR) estimated using the Modification of Diet and Renal Disease (MDRD), Cockcroft-Gault (CG), Hoek, Larsson, Filler and Le Bricon equations. Comparison was made with the nuclear GFR (nGFR) (n = 41) measured through 51-Cr EDTA clearance. Results. The mean age of recipients was 56 +/- 13 years, and they were 6.5 +/- 4.7 years post-OLT. Fifty-six percent of recipients had a nGFR < 60 mL/min/1.73 m(2). nGFR correlated significantly with all predictive equations (P < 0.001). The MDRD, CG and Le Bricon equations had the smallest degree of bias (-7.6, -7.3 and 3.4 mL/min/1.73 m(2), respectively), with 22%, 22% and 27% of estimates, respectively, being within 10% of nGFR measurements. In OLT recipients with nGFR < 60 mL/min/1.73 m(2), the degree of bias of both the creatinine-base MDRD and cystatin-based Hoek equations was within 2 mL/min/1.73 m(2) difference between the measured and estimated GFR, but 41% and 36% of estimates were within 10% of the nGFR measurement. Conclusions. Therefore, the degree of inaccuracy in cystatin C- and creatinine-based predictive equations brings into question their clinical utility in OLT recipients. We have no evidence that cystatin C is superior to creatinine in this population.