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SP01-21: Assessment of Knowledge of Warfarin therapy and Anticoagulation Control in Patients at a Tertiary Care Public Hospital

Poster Presenter

Shariva Suvarnn Ranadive

Pharmacology post graduate student
Lokmanya Tilak Municipal Medical College
India

Objectives

To assess the knowledge and anticoagulation control in patients receiving warfarin therapy and to determine the association between demographic characteristics, knowledge, adherence to therapy, self-reported adverse events and the INR control.

Method

Adult patients attending warfarin clinic were interviewed using a knowledge questionnaire (20 items) in a cross sectional study and details of warfarin therapy, ADRs and last 8 INR values were recorded. A score >75% was adequate knowledge and >60% INR values in therapeutic range was good control.

Results

Interim analysis of 77/150 consenting patients showed mean age 43.8 years and female gender in 64.9%. 24.7% of patients were uneducated and 64.9% not earning. Mean weekly warfarin dose of 34mg was received for 101.9 months (mean) for mitral valve replacement in 68.8% patients. 26% had missed their warfarin dose and 6.5% INR monitoring in the last 1 year. 51.9% reported a bleeding event of which in 15.2% it was recurrent. Ecchymosis was the most common presentation. 11.9% reported occurrence of thrombosis in past. Of the 63 patients with 8 readings of INR only 26.9% patients had a good control; majority of the poor control had INR values in sub therapeutic range. 96.1% had received the warfarin information leaflet but only 57.1% were explained about it by the clinician and only 29.9% had actually read the leaflet. Knowledge scores of only 44.1% were adequate. Though 71.4% of patients knew the name of the anticoagulant, only 54.5% were aware of the dose, frequency and colour of their warfarin tablet. 87 % and 92.2 % knew the indication and mechanism of action of warfarin respectively. 96.1% respondents were able to state the frequency of INR monitoring advised but only 40.3% could reveal the exact test name. Though only 35.1% knew their target INR, ~75 % were aware about the consequences of deranged INR. Food-drug and drug-drug interactions were known to 50.6% and 27.3% respectively. 66.2% were aware about the preventive measures to be undertaken to avoid bleeding events. Majority were aware about the precautionary measures like informing their warfarin prescriber about any new additions or deletions to their drug regime and also informing the treating doctor about warfarin therapy before interventions. The association between demographic characteristics, knowledge, adherence to therapy, self-reported adverse events and the INR control for 150 patients is pending.

Conclusion

Knowledge of warfarin therapy among patients in this study was not adequate. Only 44.1% of patients had adequate knowledge about warfarin therapy. Only 26.9% of patients had good INR control based on the INR readings. Most of the poor INR control values were in sub therapeutic range though our estimates of thrombosis are lesser than minor or major bleeding events. These estimates could be compromised due to recall bias in the survey. Adherence to warfarin therapy and monitoring was good in our patients. Most of the patients had received warfarin information leaflet but few of them read it or were counselled adequately by the clinician. This could be because majority of our study respondents comprised of females who being uneducated were dependent on the primary care giver for instructions given by the clinician. This could be reflected in their knowledge about the dose of warfarin and the monitoring test done for it. The knowledge about drug interactions due to commonly used drugs like NSAIDs is also very deficient. More reported bleeding events might be due to poor knowledge about simple preventive lifestyle measures which are not probably highlighted during the counselling. Though the association between these variables is yet to be determined(pending). We recommend that during chronic therapy with warfarin the written information should be supplemented with effective counselling of patients as well as caregivers. So in a country like India with different set of challenges, dedicated counselling to improve knowledge and modifications in warfarin leaflet to cater our patient population are mandatory.