Validity of Current Equations to Estimate Glomerular Filtration Rate in Kidney Transplant Recipients

BackgroundAssessing glomerular filtration rate (GFR) is important in surveillance of kidney transplant recipients. This study aimed to determine accuracy of current equations to estimate GFR in Arabic kidney transplant recipients versus measurement of true GFR by 99m technetion diethylene triamine pentaacetic acid (99mTc- DTPA).MethodsGFR measurements were performed in 158 adult kidney transplant recipients including 91 males (58%), age of overall mean 46 ± 13 years. There were 82 Egyptians (52%) and 76 from different Arab countries (48%). All grafts were obtained from living related kidney donors.ResultsThe serum creatinine values range from 0.7 to 8 mg/dL; the true GFR values ranged from 8 to 105 mL/min/1.73 m2. We estimated GFR using the Modification of Diet in Renal Disease (MDRD), abbreviated MDRD (aMDRD), Walser, Nankivell, Cockcroft-Gault, Mayo Clinic Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and El-Minia equations. All eight estimated eGFRs correlated with 99mTc-DTPA clearance (P < .05), but their r2 was low ranging from 0.66 to 0.53 Their respective r2 values were: MDRD 0.66, aMDRD 0.60, Walser 0.53, Nankivell 0.58, Cockcroft-Gault 0.59, Mayo Clinic 0.59, CKD-EPI 0.61, and El-Minia equation 0.61. These results were not significantly different when we restricted our analysis to those with body mass indexes < 25 kg/m2, or to Arabic non-Egyptian subjects.ConclusionsAll eight equations are far from ideal. In an unselected kidney transplantation population in the Arab area, current GFR prediction equations cannot substitute for GFR measurement.