Background: Efficacy and safety of vitamin K antagonists (VKAs) is optimised in atrial fibrillation (AF) patients when the International Normalised Ratio (INR) is 2.0-3.0. Anticoagulation control comparing different ethnic groups is limited, although epidemiological studies suggest poorer INR control in non-white cohorts.
Methods: VKA control was assessed retrospectively by time-in-the-therapeutic range (TTR) (Rosendaal method) and percentage INR-in-range (PINRR) in 991 White, Afro-Caribbean and South-Asian AF patients [overall mean (SD) age 71.6 (9.4) years; 55% male; mean (SD) CHA2DS2-VASc score 3.4 (1.6)] over a median (IQR) follow-up of 5.2 (3.2-7.0) years.
Results: Compared to Whites, mean (SD) TTR and PINRR were significantly lower in South-Asians [TTR 67.9% vs. 60.5%; PINRR 58.8% vs. 51.6%, respectively] and Afro-Caribbeans [TTR 67.9% vs. 61.3%; PINRR 58.8% vs. 53.1%, respectively], despite similar INR monitoring intensity. Logistic regression revealed non-white ethnicity [OR 2.62; 95% Confidence Interval [CI] (1.67-4.10) and OR 3.47 (1.44-8.34)] and anaemia [OR 1.65 (1.00-2.70) and OR 6.27 (1.89-20.94)] as independent predictors of both TTR and PINRR < 70%, respectively. At follow-up, 329 (33.2%) patients experienced ≥1 major adverse clinical event. Cardiovascular hospitalisation was significantly higher among South-Asians (32.3%) compared to the Whites and Afro-Caribbeans (21.3% vs 25.6% respectively).
Conclusions: Ethnic disparities in quality of anticoagulation control are evident, with South-Asians and Afro-Caribbeans having poorer control compared to Whites, despite similar intensity INR monitoring. Non-white ethnicity remained the strongest independent predictor of poor TTR and PINRR. Interventions to improve anticoagulation control need to be implemented, particularly targeting ethnic minority patients.
Keywords: Anticoagulation control; Atrial fibrillation; Ethnicity; Stroke prevention; Vitamin K antagonist.
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