Patient self-management of warfarin therapy: pragmatic feasibility study in Canadian primary care

Abstract

Objective: To investigate the effectiveness of patient self-management (PSM) of anticoagulation using warfarin in a typical primary care site in Canada and to determine the feasibility of conducting a future large-scale trial in this setting.

Design: An 8-month pragmatic open-label randomized crossover trial.

Setting: A typical Canadian primary care practice in British Columbia.

Intervention: Patients were randomized to PSM or physician management for 4 months, after which allocation was reversed. The PSM group members were instructed to monitor their serum international normalized ratio (INR) at community laboratories and to adjust their warfarin doses independently using provided nomograms. Education on warfarin dose adjustment was limited to a single 15-minute office visit.

Main outcome measures: The primary outcome was the proportion of INR values in the therapeutic range among participants. Feasibility outcomes included proportion of eligible patients consenting, patients' preference of management strategy, patients' satisfaction, and visits or phone communication with physicians regarding dose adjustment. Safety outcomes included bleeding or thromboembolic events.

Results: Eleven patients completed the trial, contributing 99 patient-months of monitoring and providing 122 INR measures. The mean proportion of INR values in therapeutic range among subjects in the PSM and physician-management groups was 82% and 80%, respectively (P = .82). The improvement in patient satisfaction with PSM was not significant. Ten of the 11 patients preferred PSM to physician management and elected to continue with this strategy after study completion (P = .001). No calls or visits were made to the physician regarding dose adjustment during the PSM period. There were no episodes of major bleeding or thromboembolic events.

Conclusion: Patient self-management was not demonstrated to be superior to standard care, but was easily implemented and was the method preferred by patients. Our feasibility outcomes justify a larger trial and suggest that subject recruitment and protocol adherence would not pose barriers for such a study. Trial registration number NCT00925028 (ClinicalTrials.gov).

Figures

Figure 1

CONSORT flow diagram CONSORT—Consolidated Standards of Reporting Trials.

Figure 2

Scatter data plot of INR values among patients in the PSM and usual care groups INR—international normalized ratio, PSM—patient self-management. *Therapeutic target range 2.0 to 3.0.