Patient adherence to warfarin therapy and its impact on anticoagulation control

Abstract

Warfarin is a commonly prescribed oral anticoagulant in Saudi Arabia and yet patient adherence to warfarin therapy and its impact on anticoagulation control have not been well researched here. A cross-sectional survey was conducted over 6 weeks at the outpatient anticoagulant clinic on patients who were receiving warfarin. Adherence was assessed using the translated Arabic version of the Morisky Medication Adherence Scale (MMAS-8). Levels of adherence were classed as low (score ⩽ 7), or high (score = 8) based on the scores. Good anticoagulation control was defined as percent Time INR in Therapeutic Range (TTR) ⩾ 75% using the Rosendaal method. A total of 192 patients completed a questionnaire with a response rate of 68.1%. It was established that no association was found between adherence to warfarin therapy and INR control groups. Among the 89 (46.4%) patients who had high adherence, only 34 (38.2%) had an acceptable INR control. This was versus 103 (53.6%) patients who had low adherence but also 34 (33.0%) had good INR control. Multivariate logistic regression (MLR) analysis showed that when studying females and occupational status of unemployment, they were independently associated with poor INR control with an OR 2.31, 95% CI 1.10-4.92, and OR 2.71, 95% CI 1.12-6.61 respectively. MLR analysis also showed that age <50 years alongside no formal education was independently associated with low adherence to warfarin therapy with an OR 2.67, 95% CI 1.29-5.52 and OR 2.63, 95% CI 1.01-6.93 respectively. The demographic background influences adherence and INR control, but no association was found between adherence and anticoagulation control.

Factors predicting self-reported medication low adherence in a large sample of adults in the US general population: a cross-sectional study

“…It has been widely used in adherence research for multiple disease states and medications across numerous countries. [14][15][16][17] In this study, the MMAS-8 was used to assess for self-reported low adherence in general and was not grounded in any specific conditions or medications. MMAS-8 scores can range from 0 to 8 with low adherence defined as a score <6, medium adherence as scores of 6 or 7 and high adherence with a score of 8.…”

Nível de informação e adesão à terapia de anticoagulação oral com varfarina em pacientes acompanhados em ambulatório de atenção primária à saúde

“…[12][13][14] Adherence was measured using the Portuguese translation of the (8-item Morisky Medication Adherence Scale, MMAS-8), which has been validated. 15,16 The MMAS-8 was originally developed to assess treatment adherence in patients with systemic arterial hypertension, but Wang et al 17 and Mayet 18 have validated it for assessing treatment adherence in patients taking warfarin. To date, there are no published studies conducted in Brazil using the MMAS-8 to assess adherence to oral anticoagulation treatment.…”

“…Studies undertaken in specialist anticoagulation clinics using the MMAS-8 exhibited a higher percentage of patients with treatment adherence (from 34.5% 17 to 46.4% 18 ). Other studies, also conducted in specialist services, but using the 4-item Morisky Medication Adherence Scale (MMAS-4), 26 found treatment adherence rates of 39% to 50%.…”

“…Studies conducted in oral anticoagulation settings have identified similar frequencies, from 64 to 75%, 3,6,8,18 contradicting the expectation that care at a specialist clinic would result in better control of anticoagulation levels, with lower frequencies of patients outside the therapeutic range.…”

“…This result is in line with other studies, that also failed to detect significant associations, not even with variables related to knowledge 3,6,14 or treatment adherence. 3,18 One limitations affecting this study is related to conducting PT tests once only. The number of participants was low; but attempts were made to enroll all patients cared for by PHC who were taking warfarin in the municipal district of Ijuí.…”