Concordance of Chronic Kidney Disease Stage and Metformin Management Using CKD-EPI 2021 Race-Free Equation vs CKD-EPI 2009 Equation to Estimate Glomerular Filtration Rate.

Abstract

To the Editor: Metformin is a first-line agent for the treatment of hyperglycemia in type 2 diabetes. However, the risk of lactic acidosis necessitates close monitoring of renal function (1). The Kidney Disease: Improving Global Outcomes (KDIGO) organization clinical practice guidelines recommend using an estimation of glomerular filtration rate (eGFR) to assess renal function, categorize chronic kidney disease (CKD) stage, and guide metformin management (2). Multiple professional organizations have recommended implementation of the new CKD Epidemiology Collaboration (CKD-EPI) 2021 race-free eGFR equation, calculated from creatinine (eGFRcr), that does not disproportionately affect any one group of individuals (35). In order to assess the potential impact of implementation, a retrospective analysis was performed to determine concordance of CKD stage and metformin management categories using the CKD-EPI 2021 vs CKD-EPI 2009 eGFRcr equations. Creatinine concentration (first result used if multiple measurements available), age, hemoglobin A1c (HbA1c), and race from patients 18 years old with an active metformin medication between April 1, 2021, and July 1, 2021, were retrieved from the electronic health record. eGFRcr was calculated from reported serum creatinine (mg/dL) using both the CKD-EPI 2021 and CKD-EPI 2009 equations. Concordance, defined as the number (percentage) of eGFRcr values that fell into the same CKD stage and metformin management categories using each equation, was evaluated in both self-reported Black and non-Black patients. Patients whose race was listed as unknown in the medical record were excluded. Metformin management recommendation categories were defined according to the KDIGO Clinical Practice Guidelines for the Evaluation and Management of Chronic Kidney Disease. KDIGO recommends continuing metformin use in patients with an eGFRcr 45 mL/min/1.73 m2 (CKD-1 to -3a), reviewing use for potential dosage adjustments with an eGFRcr 30 to 44 (CKD-3b), and discontinuing use when eGFRcr is 30 (CKD-4 to -5).