Metformin-eligible patient population according to eGFR or serum creatinine level

Abstract

Introduction: The metformin label has recently been changed from serum creatinine (sCr)-based to estimated glomerular filtration rate (eGFR)-based indication, which is expected to expand its use for patients with mild renal insufficiency. However, because the sCr level is lower in Asians than in Caucasians at the same level of renal function, this change might not expand metformin use in the Asian population. In addition, the elderly population is of special concern because the sCr level is lower in the elderly population than in the younger population at a same level of renal function. We investigated the effect of this change among Korean patients with diabetes. Methods: Data from the Korean National Health and Nutrition Examination Survey 2009 to 2014 were used and included 4,127 adult patients with diabetes including 1,912 elderly patients aged 65 years or older. The metformin eligibility was assessed by the sCr level (1.4 mg/dL for women and 1.5 mg/dL for men) or by eGFR categories (contraindicated, <30

indeterminate, ≥30, <45

likely safe, ≥45 mL/min/1.73 m2) calculated by various eGFR equations including MDRD equation. We designated the expanding and contracting population as those who are likely safe according to eGFR among sCr-ineligible patients and those contraindicated according to eGFR among sCr-eligible patients, respectively. Results were weighted to the whole Korean adult population. Results: Among total diabetic patients, all eGFR equations showed expansion in the population for whom metformin is likely safe, ranging from 14.3% to 19.9% of the sCr-ineligible population. With the MDRD equation, the expanding population was 15,264 (15.8%) and the contracting population was 0 (0.0%). Male sex and younger age were significantly associated with the expanding population. For elderly diabetic patients, all eGFR equations also showed expansion in likely safe group of metformin use, ranging from 4.1% to 16.8% of the sCr-ineligible group, and the contracting population was 0%. Conclusions: Contrary to our concern, prescribing metformin according to eGFR substantially expanded the indication of its use among the Korean diabetic patients including the elderly patients.