Cystatin C-based Formula is Superior to MDRD, Cockcroft-Gault and Nankivell Formulae in Estimating the Glomerular Filtration Rate in Renal Allografts

Abstract

Objectives: There are conflicting reports on the reliability of the various glomerular filtration rate formula in renal allografts, to assess the performance of various glomerular filtration rate formula in estimating renal function of renal allografts.

Materials and Methods: Glomerular filtration rate was measured using an isotope Tc99m DTPA in 97 renal transplant patients and estimated using modification of diet in renal disease, Cockroft-Gault formula, Nankivell, and a cystatin C-based formula. The overall performance of these formula was evaluated by calculating bias, accuracy and precision.

Results: Mean age was 39.8 years (± 12.7), body mass index was 26.9 (± 6.3) and serum creatinine was 114.5 µmol/L (± 39.3). The mean measured glomerular filtration rate was 58.1 mL/min (± 25.6). The bias with modification of diet in renal disease was 7.7 (P = .03), with Cockroft-Gault formula it was 3.2 (P = .3), with Nankivell it was 10.3 (P = .0002), and with cystatin C it was 0.31 (P = .9) The precisions (r) for modification of diet in renal disease, Cockroft-Gault formula, Nankivell, and cystatin C were 0.26 (P = .01), 0.26 (P = .01), 0.42 (P = .0001), and 0.60 (P < .0001), respectively. We also investigated the impact of sex, age, body mass index, and glomerular filtration rate on the performance of these 4 formula.

Conclusion: The best correlation, highest precision, accuracy, and least bias were seen when using cystatin C. The largest bias was seen when using Nankivell and modification of diet in renal disease formula.