Estimating glomerular filtration rate in kidney transplant recipients: performance over time of four creatinine-based formulas.

BACKGROUND: The management of kidney transplant recipients requires accurate estimate of glomerular filtration rate (GFR). This study aims at evaluating the performance of four creatinine-based formulas for estimating the GFR (estimated GFR) in this population.

METHODS: Performances of Cockcroft and Gault formula, Modification of Diet in Renal Disease (MDRD) simplified formula, Chronic Kidney Disease Epidemiology Collaboration formula, and Nankivell formula were assessed compared with inulin clearance taken as the gold standard for measuring GFR (measured GFR). Performances were assessed using the first measurements of GFR obtained in 1249 subjects. How estimated GFR tracks changes in measured GFR over time since transplantation in those patients with repeated measures was also assessed.

RESULTS: The MDRD formula provided the best estimate of GFR with a mean bias of -0.5 mL/min/1.73 m, a standard deviation of bias of 12 mL/min/1.73 m, and a 30% accuracy at 85%. The MDRD formula also seemed to provide the best performance for estimating GFR, irrespective of age, stage of renal failure, and in people whose body mass index was more than 18.5 kg/m. This robustness is important in clinical practice. The performance of the four formulas was not modified by the posttransplant period.

CONCLUSION: Even if 30% accuracy was suboptimal in the Kidney Disease Outcomes Quality Initiative guidelines, our results, obtained in a large number of patients, lead us to recommend using the MDRD formula to monitor GFR in kidney transplant recipients.