INTRODUCTION
Anticoagulation is used to treat and prevent venous thrombosis and to prevent intracardiac thrombosis due to some structural heart diseases or dysrhythmias. Depending on the indication, treatment may be lifelong. Over-anticoagulation may result in bleeding and under-coagulation in thrombotic complications, including stroke. With the advent of direct oral anticoagulants (DOACs), there is increased choice of drugs available. However, vitamin K antagonists such as warfarin remain the most widely used oral anticoagulants, and form the focus of this article.
When using vitamin K antagonists, the degree of anticoagulation is measured by the international normalised ratio (INR), and a patient’s longitudinal anticoagulation control can be described by the proportion of INRs which fall in the therapeutic range (PTR), or by the proportion of time spent in the therapeutic range (TTR), interpolating INR results for the time between actual INR measurements. Patients in sub-Saharan Africa (SSA) have poor anticoagulation control as measured by their PTR/TTR, which is evident from trials,[1–3] large multisite registries,[4,5] and smaller observational studies (Table 1).
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In this review, we explore potential reasons for this poor anticoagulation control.