A cross-sectional evaluation of five warfarin anticoagulation services in Uganda and South Africa

Abstract

Introduction Warfarin is the most commonly prescribed oral anticoagulant in sub-Saharan Africa and requires ongoing monitoring. The burden of both infectious diseases and non-communicable diseases is high and medicines used to treat comorbidities may interact with warfarin. We describe service provision, patient characteristics, and anticoagulation control at selected anticoagulation clinics in Uganda and South Africa. Methods We evaluated two outpatient anticoagulation services in Kampala, Uganda and three in Cape Town, South Africa between 1 January and 31 July 2018. We collected information from key staff members about the clinics' service provision and extracted demographic and clinical data from a sample of patients' clinic records. We calculated time in therapeutic range (TTR) over the most recent 3-month period using the Rosendaal interpolation method. Results We included three tertiary level, one secondary level and one primary level anticoagulation service, seeing between 30 and 800 patients per month. Care was rendered by nurses, medical officers, and specialists. All healthcare facilities had on-site pharmacies; laboratory INR testing was off-site at two. Three clinics used warfarin dose-adjustment protocols; these were not validated for local use. We reviewed 229 patient clinical records. Most common indications for warfarin were venous thrombo-embolism in 112/229 (49%), atrial

Improving anticoagulation in sub-Saharan Africa -- what are the challenges, and how can we overcome them?

“…However, centralisation can even bypass people in urban settings, as illustrated in some of the examples in Figure 1. Centralised laboratory INR testing also means that results are delivered with a long turn-around time, [27] and that patients may be required to attend separate blood sampling and INR monitoring visits, [22,87] driving up the expenses they incur.…”

“…[9] In the Namibian example, more than half of patients with an INR >4 were over-corrected so that their subsequent INR was subtherapeutic. [19] Warfarin formulations other than 5mg are frequently not available in SSA, [6,22] making precision dosing difficult. Complicated weekly dosing schedules of alternating daily dosages which often require tablet splitting (sometimes into quarters) are used, potentially compromising the actual dose taken.…”

“…In SSA, antiretroviral therapy is a significant source of potential drug-drug interactions. [18,20,22,70,92,93,105] Tuberculosis is also common in SSA, and rifampicin use induces multiple cytochrome P450 isoforms resulting in a reduced warfarin effect. In a Kenyan case series of patients on concurrent rifampicin and warfarin, the median warfarin dose increase with rifampicin was 16%, but some patients required dose increases up to +441%.…”

“…Anticoagulation patients in SSA are younger than those in high-income settings. For example, in Uganda and South Africa the median age of patients attending five anticoagulation services was 56 years, [22] and in a Kenyan service the mean age was 43 years. [20] Younger patients often show reduced adherence compared to older patients.…”

Evaluation of Stable Doses of Warfarin in a Patient Cohort

“…Variations in such protocols were observed in a developing nation that led to poor anticoagulation control amongst patients taking warfarin. [19] Bayesian forecasting and several machine learning tools ▶table 4 Comparison of administered and IWPC algorithm predicted doses in various categories. $ -Between administered initial doses; @ -between IWPC algorithm predicted doses; # -between the percent differences between the doses; * -statistically significant (P < 0.05); IWPC -International warfarin pharmacogenetic consortium; Ω -between administered initial and IWPC predicted doses in males;£ -between administered initial and IWPC predicted doses in females; α -between administered initial and IWPC predicted doses in middle aged; β -between administered initial and IWPC predicted doses in older adults; ¥ -between administered initial and IWPC predicted doses in elderly.…”