Estimated Glomerular Filtration Rate Bias in Participants with Severe Obesity Regardless of Deindexation.

Abstract

Morbid obesity is associated with a higher independent risk of chronic kidney disease (CKD). Estimated glomerular filtration rate (eGFR) has been evaluated in a limited number of studyparticipants with severe obesity. A total of 706 measured GFR (mGFR) results from 598 participants with obesity (BMI ≥ 35 kg/m2 )were retrospectively collected. The performanceof the Modification of Diet in Renal Disease (MDRD)equation, Chronic Kidney Disease-Epidemiology (CKD-EPI)equation, and deindexed eGFR were compared with mGFRfrom thegold standard technique (inuline or iohexol), adjusted (mGFRr) or nonadjusted (mGFR) to body surface area. Absolute bias, precision, and accuracy were calculated. Mean mGFRr (58 ± 31 mL/min/1.73m2 ) was significantly different from CKD-EPI and MDRD (P < 0.001). Mean mGFR (nonindexed) (70 ± 40 mL/min) was significantly higher than mGFRr (P < 0.001). eGFR showed important biases and low accuracies for CKD-EPI and MDRD (10.7 ± 10.7 and 12.2 ± 13.7 mL/min/1.73m2 ; 78% vs. 75% respectively). Deindexation worsened bias and accuracy 30% (percentage of GFR estimates within 30% of mGFRr or mGFR) between eGFR and mGFR. eGFR overestimates mGFR and is associated with important biases and inaccuracies in patients with severe obesity, and deindexing eGFR worsens the overestimation. These findings may have important implications in examining kidney function inpatients with obesity.