Comparison between creatinine and cystatin C-based GFR equations in renal transplantation

Background. Estimation of glomerular filtration rate ( GFR) from serum creatinine ( S-cr) or cystatin C ( Cys C) exhibit variable performances. Methods. We compared the performances of 14 Scr and 9 Cys C estimated GFR equations using inulin clearance ( Cl-in) as the reference test in 103 stable renal transplant populations. Bias, precision, receiving operation characteristics ( ROC), accuracy within 30% ranges from the reference method and agreements of each test were compared. Results. Mean Clin was 46.4 +/- 20.9 ml/ min/ 1.73 m(2). S-cr and Cys C levels correlated well with each other ( r=0.83, P< 0.0001) and with Cl-in ( r =- 0.57 and -0.53, P< 0.001, respectively). ROC analysis demonstrated no superiority of Cys C over Scr. Gats equation achieved the highest accuracy of 70% in patients with GFR >= 60 ml/ min/ 1.73m(2). In patients with GFR >= 60 ml/ min/ 1.73 m(2), the Nankivell equation demonstrated the highest accuracy of 73.91%. Cys C- based equations were not depicted to be thoroughly accurate. Bias, precision and agreement were otherwise similar in all GFR tests. Conclusion. S-cr- based equations did not appear to be inferior to Cys C- based equations as a means to estimate GFR in renal transplant patients.