Removal of the race coefficient and adjustment to individual BSA provide the most accurate estimation for GFR in Black adolescents

Introduction: Obesity is more prevalent among minorities, increasing the risk for cardio-renal morbidity. We explored interactions between race, body mass index (BMI), and the risk of hyperfiltration associated with Obesity Related Glomerulopathy (ORG). Methods: We created a cohort of women and girls ages 12 to 21 from the New York Metropolitan area using electronic health records. Glomerular filtration rate (GFR) was estimated in three ways: I) using the standard age recommended formulae, II) eGFRr: without a race-specific coefficient, and III) Absolute eGFRr: combing removal of the race coefficient and adjusting to individual body surface area. Multivariate logistic regression was used to analyze the relative contribution of risk factors for ORG associated hyperfiltration, defined by a threshold of 135ml/min/1.73m2. Bland Altman analysis and Pearsons coefficient assessed the correlation of each formula with creatinine clearance (CrCl). Results: 7315 Black and 15,102 non-Black women and girls had simultaneous evaluation of kidney function and body measures. CrCl was available in 207 non-Black and 107 Black individuals as an internal validation. Simultaneous removal of the race coefficient and adjustment to individual BSA estimated GFR most accurately compared to CrCl, across BMI groups and between races. Hyperfiltration was more frequent in obese Black compared to non-Black individuals when using standard eGFR (20% vs. 6.5% respectively) but had a lower frequency after eliminating the race-specific coefficient (4.5% vs. 6.5%). Black race was independently associated with a higher risk of hyperfiltration with standard eGFR calculations (OR=3.43, 95% CI 2.95-3.99) and with lower risk when estimated by eGFRr (OR=0.56, 95% CI 0.45-0.70). Simultaneous removal of the race coefficient from GFR calculation and adjustment to individual BSA attenuated the difference in risk between races (OR=0.8, 95% CI 0.68-0.94). The combined correction agreed well with creatinine clearance (Pearson's correlation coefficient r=0.64, 0.52 and 0.52 for absolute eGFRr, eGFR and eGFRr respectively. Conclusions: Removal of the race coefficient from GFR estimating equations obscures obesity associated hyperfiltration among Black adolescents. This correction should be accompanied by adjustment to individual BSA to improve estimation of GFR to avoid misclassification of obesity related hyperfiltration.