Performance of estimated glomerular filtration rates to monitor change in renal function in kidney transplant recipients.

BACKGROUND: Glomerular filtration rate estimates (e-GFR) are often used to evaluate the changes in renal function, but have not been validated for this purpose in kidney transplant recipients (KTRs). The aim of this study was to evaluate the validity of e-GFR for monitoring serial changes in renal function in KTR using directly measured GFR by inulin clearance (I-GFR) as the reference standard. METHODS: Performances of inverse serum creatinine (1/creat) and Cockcroft and Gault, Modification of Diet in Renal Disease, and Chronic Kidney Disease Epidemiology Collaboration formulas were assessed to estimate the changes in I-GFR. RESULTS: A total of 1935 I-GFR clearance procedures were performed in 631 KTRs who underwent serial measurements between 2003 and 2009. The baseline median I-GFR were 51.0 mL/min/1.73 m(2) (confidence interval 95%: 23-84 mL/min/1.73 m(2)]. The performances of 1/creat and formulas for detecting the I-GFR variations between two consecutive measurements (n = 1304) were similar. To detect the variations of <20% (increase or decrease), sensitivities ranged between 50 and 56%, and specificities between 64 and 69%. To detect the variations >20% (increase or decrease), sensitivities ranged between 27% and 39%, and specificities between 88 and 97%. Bland-Altman plots confirmed the scattering of values for individual patients. CONCLUSIONS: In a population of Caucasian KTRs, the mean changes in GFR are correctly estimated whatever the formula used in the range of 23-84 mL/min/1.73 m(2) and can thus be applied in population studies. However, in clinical practice, individual changes in GFR evaluated by formulas should be interpreted with caution in KTRs.

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.