Abstract
Purpose: To assess the level of knowledge on warfarin therapy and anticoagulation control, and explore the association between knowledge and anticoagulation control in a section of Saudi population. Methods: A cross-sectional prospective survey was conducted over a 4-week period in 2013 at King Khalid University Hospital outpatient anticoagulant clinic in Riyadh, Saudi Arabia. Adult patients who were either discharged on warfarin or taking warfarin and attending the outpatient anticoagulant clinic for ≥ 6 months were invited to participate in the study. A questionnaire was used to collect the demographic data and knowledge of warfarin therapy (8-item). International Normalized Ratio (INR) readings were obtained from electronic-laboratory database. Good knowledge of warfarin was defined as a score of ≥ 75 % and good (INR) control was defined as ≥ 75 % Time INR in therapeutic range (TTR) calculated using Rosendaal method. Results: A total of 105 patients completed the questionnaire with a response rate of 49.2 %. Seventy nine patients (75.2 %) had good knowledge of warfarin (scored ≥ 75 %), but only 35 patients (33.3 %) had good anticoagulation control (TTR ≥ 75 %). An association was observed between patients with no formal education and poor warfarin knowledge (p = 0.012). Smoking history was also linked with warfarin knowledge (p = 0.025). INR control results significantly differed by marital status with divorced/widow status displaying poor INR control (p = 0.028). Lastly, no association was found between good knowledge and good INR control (OR 1.35, 95 %; CI 0.537 – 3.392). Conclusions: The majority of patients seen at the outpatient anticoagulation clinic have good knowledge of warfarin therapy although only a third showed good anticoagulation control. The results indicate no significant association between knowledge of warfarin therapy and anticoagulation control. Studies with a larger sample size are recommended to verify the foregoing results. Keywords: Oral Anticoagulant, Warfarin, International Normalized Ratio, Knowledge, Anticoagulation Control
Highlights
Warfarin is the most widely used anticoagulation drug worldwide including Saudi Arabia due to its ease of administration and low cost
A total of 232 patients attended the outpatient anticoagulation clinic during study period and out of this figure, 118 patients accepted to partake in the study which is a response rate of 49.2 %
The results showed that 74.1 % of patients had good knowledge of warfarin, which is comparable to the findings in this study [18]
Summary
Warfarin is the most widely used anticoagulation drug worldwide including Saudi Arabia due to its ease of administration and low cost. The drug has a very low narrow therapeutic index and it provides effective anticoagulation for the treatment of thromboembolic conditions. Warfarin has a fair safety and a tolerability profile providing that INR levels are kept within therapeutic range. The improper use of warfarin is associated with unintentional bleeding and thrombosis as well as the lack of patients' knowledge, concurrent disease states, diet, and poor adherence to warfarin therapy [2,3,4]. Warfarin-associated intracerebral hemorrhage [5], with a 50 % mortality rate, is one of the most severe adverse drug events (ADEs). Unintended thromboembolic events have been reported as a result of inadequate anticoagulation. In 2013, Chen et al reported that high-risk patients, who were not compliant with warfarin therapy, had risks which were three times greater of VTE recurrence [7]
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