Obesity Related Glomerulopathy in adolescent women: the effect of Body Surface Area

Background: Adolescent obesity, a risk factor for cardio-renal morbidity in adulthood, has reached epidemic proportions. Obesity-related glomerulopathy (ORG) has an early reversible stage of hyperfiltration. Age-appropriate formulae for estimated glomerular filtration rate (eGFR), which are standardized to ideal body surface area (BSA) and provide assessment of kidney function in mL/min/1.73 m2 units, may underestimate prevalence of early ORG. We investigated whether adjusting eGFR to actual BSA more readily identifies early ORG. Methods: We studied a cohort of 22,417 young individuals ages 12-21 years from a New York metropolitan multi-institutional electronic health records clinical data base. eGFR was calculated in two ways: BSA-standardized eGFR; and absolute eGFR. Hyperfiltration was defined above a threshold of 135mL/min/1.73 m2 or 135 mL/min, respectively. The prevalence of hyperfiltration according to each formula was assessed in parallel to creatinine clearance. Results: Serum creatinine values and hyperfiltration prevalence according to BSA-standardized eGFR were similar, 13.4-15.3%, across Body Mass Index (BMI) groups. The prevalence of hyperfiltration determined by absolute eGFR differed across BMI groups: Underweight - 2.3%; Normal 6.1%; Overweight - 17.4%; Obese - 31.4%. This trend paralleled the rise in creatinine clearance across BMI groups. Conclusions: Absolute eGFR more readily identifies early ORG than the currently used formulae, which are adjusted to a standardized BSA, not representative of current population BMI measures. Using Absolute eGFR in clinical practice and research may improve the ability to identify, intervene and reverse early ORG, which has great importance with increasing obesity rates.