Full age spectrum equation versus CKD-EPI and MDRD equations to estimate glomerular filtration rate in adults with obstructive nephropathy

Objective To compare the full age spectrum (FAS) equation with the Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in predicting glomerular filtration rate (GFR) in patients with obstructive nephropathy. Methods Adult patients with obstructive nephropathy who had undergone a GFR measurement using technetium-99m diethylenetriaminepentaacetic acid radioisotope renography were enrolled in the study. The measured GFR was taken as the reference value. Bias, precision and accuracy were compared between the three equations. Kappa test and the Bland-Altman method were used to evaluate the classification and the agreement. Receiver operating characteristic (ROC) curve analysis was used to describe the diagnostic accuracy of each equation. Results A total of 327 patients were enrolled. The P30 value for the FAS equation was 60.2% in the overall study cohort. The FAS equation had the highest diagnostic accuracy (ROCAUC = 0.87, 95% confidence interval [CI] 0.84, 0.91) compared with the MDRD equation (ROCAUC = 0.86, 95% CI 0.82, 0.89). The median bias of the FAS equation was significantly higher than that of the MDRD equation (8.7 versus 7.6 ml/min/1.73 m(2), respectively). Conclusions Despite the drawbacks associated with each equation, the FAS equation was probably closer to ideal to estimate GFR in patients with obstructive nephropathy.