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

IntroductionWarfarin 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.MethodsWe 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.ResultsWe 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 fibrillation in 74/229 (32%) and valvular heart disease in 30/229 (13%). Patients were generally followed up monthly. HIV prevalence was 20% and 5% at Ugandan and South African clinics respectively. Cardiovascular comorbidity predominated. Furosemide, paracetamol, enalapril, simvastatin, and tramadol were the most common concomitant drugs. Anticoagulation control was poor at all included clinics with median TTR of 41% (interquartile range 14% to 69%).ConclusionsTTR was suboptimal at all included sites, despite frequent patient follow-up. Strategies to improve INR control in sub-Saharan patients taking warfarin are needed. Locally validated warfarin dosing algorithms in Uganda and South Africa may improve INR control.引言：华法林（Warfarin）是撒哈拉以南非洲地区最常用的口服抗凝药，且需持续开展监测。该地区传染病与非传染病的疾病负担沉重，用于治疗合并症的药物可能与华法林发生相互作用。本研究对乌干达与南非的选定抗凝门诊的服务开展情况、患者特征及抗凝控制效果进行描述。 方法：本研究于2018年1月1日至7月31日期间，对乌干达坎帕拉的2家门诊抗凝服务机构及南非开普敦的3家此类机构进行评估。我们从核心工作人员处收集门诊服务开展相关信息，并从患者门诊病历样本中提取人口统计学及临床数据。采用罗森达尔插值法（Rosendaal interpolation method）计算患者近3个月的治疗范围时间（TTR）。 结果：本研究共纳入5家抗凝服务机构，其中3家为三级医疗、1家为二级医疗、1家为一级医疗，月接诊量介于30至800例之间。诊疗工作由护士、全科医师及专科医师承担。所有医疗机构均设有院内药房；其中2家机构的实验室国际标准化比值（INR）检测需在院外开展。3家门诊采用华法林剂量调整方案，但此类方案未针对本地使用场景进行验证。本研究共回顾229份患者临床病历。华法林用药最常见的适应证为静脉血栓栓塞症（112/229，49%）、心房颤动（74/229，32%）及瓣膜性心脏病（30/229，13%）。患者通常接受月度随访。乌干达门诊的HIV感染率为20%，南非门诊为5%。心血管合并症占比最高。呋塞米、对乙酰氨基酚、依那普利、辛伐他汀及曲马多为最常见的合并用药。所有纳入门诊的抗凝控制效果均较差，TTR中位数为41%（四分位间距14%~69%）。 结论：尽管患者随访频率较高，但所有纳入机构的TTR均未达最优。亟需制定针对撒哈拉以南非洲地区华法林使用者的INR控制改善策略。乌干达与南非经本地验证的华法林给药算法或可改善INR控制效果。