Determinants of Compliance with Anticoagulation: A Case-Control Study

https://doi.org/10.1016/S0002-9343(97)90048-6Get rights and content

Abstract

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 non-white (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.

Section snippets

Study Design

We conducted this study in the Anticoagulation Therapy Unit (ATU) at Massachusetts General Hospital, a large urban teaching hospital. Cases were patients who had demonstrated such severe noncompliance with chronic anticoagulation therapy that it was no longer considered safe. Controls were compliant patients attending the ATU. In-depth telephone surveys were completed with all patients. The study was approved by the Human Subjects Committee of the Institutional Review Board at Massachusetts

Demographic Features

The mean age of noncompliant cases was 53.7 years, significantly younger than the mean age of 68.7 years among controls (P <0.0001)(Table 1). The striking effect of age on compliance is displayed in the Fig. 1 in which the entire sample is divided into six groups based on quintiles of age among the controls. Because the majority of noncompliant cases were clustered in the youngest quintile, we split this group into two deciles. Using the oldest group as a reference category, noncompliant cases

Discussion

Warfarin can be a highly effective preventive therapy but careful patient compliance with medication dose and prothrombin time testing is essential to optimizing its impact. Poor compliance with anticoagulants has been documented in randomized trials1, 2and is a frequently cited concern of physicians.[11]Nonetheless, ours was the first study to explore patient features associated with noncompliance with anticoagulation.

In general, previous compliance studies have focused on rates of medication

Acknowledgements

We gratefully acknowledge the assistance of Mary A. Sheehan, RN, Robert A. Hughes, MD, and the staff of the Anticoagulation Therapy Unit at Massachusetts General Hospital.

The research reported in this paper was supported in part by a grant from the Eliot B. Shoolman Fund, Massachusetts General Hospital, Boston, Massachusetts. Dr. Arnsten was a fellow of the Harvard General Internal Medicine Fellowship Program, U.S. Department of Health and Human Services National Research Services Award Grant

References (24)

  • M Kutner et al.

    Physicians' attitudes toward oral anticoagulants and antiplatelet agents for stroke prevention in elderly patients with atrial fibrillation

    Arch Intern Med.

    (1991)
  • TR Lancaster et al.

    The impact of long-term warfarin therapy on quality of life: evidence from a randomized trial

    Arch Intern Med.

    (1991)

    • Cited by (0)

    View full text
    Copyright © 1997 Elsevier Science Inc. All rights reserved.