Determinants of compliance with anticoagulation: A case-control study

BACKGROUND: The number of patients for whom long-term anticoagulation is indicated has increased dramatically over the past decade. Good patient compliance is necessary to safely realize the benefits of anticoagulation, yet barriers to compliance with anticoagulation therapy have not been studied. METHODS: We conducted a case-control study in the Anticoagulation Therapy Unit (ATU) at Massachusetts General Hospital. Forty-three patients who had been discharged from the ATU for noncompliance (cases) and 89 randomly selected compliant ATU controls were interviewed. Noncompliant cases had self discontinued warfarin or were taking warfarin with inadequate monitoring of international normalized ratio (INR) levels. Telephone interviews assessed sociodemographic features, indication for anticoagulation, patient satisfaction, and health beliefs. RESULTS: Noncompliant cases were more likely to be younger (mean 53.7 years versus 68.7 years, P <0.0001), male (odds ratio [OR] 3.5, 95% confidence interval [CI] 1.5, 8.2), and nonwhite (OR 6.4, 95% CI 1.9, 21.9), and less likely to have had a stroke or transient ischemic attack (OR 0.2, 95% CI 0.1, 0.7). In open-ended questioning, cases were more likely to report that they did not know why warfarin had been prescribed (OR 4.4, 95% CI 1.4, 14.2). Noncompliant cases were more likely not to have a regular physician (OR 11.1, 95% CI 3.6, 50.0); among patients with a regular physician, noncompliant cases were more likely to feel dissatisfied. Examination of health beliefs revealed that noncompliant cases felt more burdened by taking warfarin, and perceived fewer health benefits. CONCLUSIONS: Patients who are noncompliant with warfarin share distinctive clinical characteristics. Notably, younger, male patients who have not experienced a thromboembolic event are more likely to forego INR testing or to stop anticoagulation therapy completely. Improved patient education, physician involvement, and ease of monitoring may improve compliance, particularly among younger male patients.