Performance of Glomerular Filtration Rate Estimating Equations Before and After Bariatric Surgery
Alex R. Chang, Jason George, Andrew S. Levey, Josef Coresh, Morgan E. Grams, Lesley A. Inker
Abstract
RATIONALE & OBJECTIVE: Evaluation of glomerular filtration rate (GFR) is challenging in adults undergoing bariatric surgery because creatinine and cystatin C levels are influenced by changes in muscle and fat mass. Additionally, indexing of GFR by body surface area (BSA) may by affected by decreases in BSA. STUDY DESIGN: Prospective observational study. SETTING & PARTICIPANTS: who underwent measurement of GFR before and after bariatric surgery. OUTCOMES: Indexed and nonindexed GFRs measured (mGFRs) using plasma iohexol clearance, indexed and nonindexed estimated GFR (eGFR) based on levels of creatinine, cystatin C, or both from Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. ANALYTIC APPROACH: ) for estimating equations were examined. RESULTS: was unbiased before (median bias, -6.0 [95% CI, -11.0 to 1.0] mL/min) and after surgery (-2.0 [95% CI, -8.8 to 4.9] mL/min). Findings were similar for indexed eGFR compared with indexed mGFR. LIMITATIONS: Small, mostly white sample. CONCLUSIONS: because of opposite biases in estimating mGFR.