The influence of renal impairment and race on maintenance warfarin dosing in a multi-ethnic Southeast Asian population

Abstract

Background Warfarin remains an important anticoagulant in certain patient groups. Though primarily liver-metabolised, recent research suggests renal function influences warfarin dosing. This has yet to be explored in a Southeast Asian population. Objectives To investigate the impact of renal impairment and ethnicity on warfarin dosing in a multi-ethnic Asian population. Methods A retrospective cohort analysis on patients seen at the institution’s anticoagulation clinic (ACC) between 2010 and 2019 was conducted. Results Among 3610 eligible patients, 70.7% had no/ mild renal impairment (eGFR≥60 ml/min/1.73m2), 24.7% had moderate renal impairment (eGFR 30 to <60ml/min/1.73m2), and 4.5% had severe renal impairment (eGFR<30 ml/min/1.73m2). Patients with moderate renal impairment required a 19% lower maintenance warfarin dose (β = 0.81, 95% CI 0.79–0.84, p < .001), and those with severe renal impairment needed a 30% lower dose (β = 0.70, 95% CI 0.66–0.75, p < .001) compared to patients with normal kidney function. Ethnically, 84.4% were Chinese, 9.5% Malay, and 6.1% South Asian. Compared to Chinese, Malays required an 18% larger maintenance dose (β = 1.18, 95% CI 1.12–1.23, p < .001), and South Asians needed an 83% larger dose (β = 1.83, 95% CI 1.73–1.94, p < .001). Compared to patients with normal renal function of the same race, South Asians with impaired renal function required a 16% lower dose, while Malay and Chinese patients needed 21% and 23% lower doses, respectively. Conclusion In this large multi-ethnic Asian study, renal function and ethnicity significantly affected maintenance warfarin dosing. South Asian patients required larger doses but were less affected by renal impairment compared to Chinese and Malays.