Introduction

Unstable anticoagulation represents an important and frequent risk factor of warfarin treatment. Problematic compliance has been suggested as possible cause of unstable anticoagulation. As part of a larger study investigating determinants of anticoagulation control of patients on warfarin, patients' behaviours towards warfarin treatment and underlying factors leading to such a behaviour, including level and desire for information, were explored.

Method

A structured interview with a random sample of 162 attenders of an anticoagulation clinic was conducted. The interview schedule contained tested scales: Medication Adherence Report Scale¹ (MARS), Intrinsic Desire for Information² (IDI), Beliefs about Medication Questionnaire³ (BMQ) and 7-question warfarin battery⁴, and 29 original questions.

Results

On MARS, 68% scored 30 (full compliance), further 24% scored 29 (rarely forgot to take warfarin). 99% took warfarin at the same time of a day, 72% within one hour, 76% in the evening. 50% reported awareness of certain dietary and lifestyle requirements, mostly alcohol consumption. 52% did not know whether warfarin was beneficial to their health. 52% believed that warfarin would protect their future health. Distribution of IDI scores was normal, with the mean of 19.2 (theoretical mean = 18) and range 10 to 30 (theoretical range = 6 to 30). Distribution of BMQ scores was normal but skewed: 88% scored above the theoretical mean.

Discussion

Patients reported high adherence to their medication and drug regime, despite gaps in knowledge about treatment and uncertainty about its benefits. High scoring on BMQ suggested trust in the traditional medication-based approach to therapy. The lack of patient knowledge identified (few patients were aware of dietary recommendations with warfarin treatment) could have important consequences for the patients' treatment. However, as identified from IDI scores, some patients lacked desire for information. In order to secure safe and effective therapy, approaches to provision of this information should be adjusted for different types of patients with respect to patients' specific desire for information.

References

1. Horne, R. & Weinman, J. 1999, "Patients' beliefs about prescribed medicines and their role in adherence to treatment in chronic physical illness", J.Psychosom.Res. , vol. 47, no. 6, pp. 555-567.

2. Duggan, C. & Bates, I. 2000, "Development and evaluation of a survey tool to explore patients' perceptions of their prescribed drugs and their need for drug information", The international Journal of Pharmacy Practice , vol. 8, no. March, pp. 42-52.

3. Horne, R., Weinmann, J., & Hankins, M. 1999, "The Beliefs about Medicines Questionnaire (BMQ): a new method for assessing cognitive representations of medication", Psychology and Health , vol. 10, pp. 1-29.

4. Arnsten, J. H., Gelfand, J. M., & Singer, D. E. 1997, "Determinants of compliance with anticoagulation: A case-control study", The American Journal of Medicine , vol. 103, no. July, pp. 11-17.