Weekly home INR testing comparable to monthly clinic testing
Drug company information might influence prescribing habits
Weekly home testing of international normalized ratio (INR) offers similar efficacy to monthly, high-quality tests in a clinic for preventing strokes and other major events, as well as modest improvements in patient satisfaction, quality of life and time within the therapeutic range, reports a study.
The Veterans Affairs Cooperative Studies Program conducted The Home INR Study (THINRS) and reported results in the Oct. 21 New England Journal of Medicine.
The prospective, randomized, nonblinded trial assigned 2,922 patients taking warfarin because of mechanical heart valves or atrial fibrillation and who were competent in the use of point-of-care INR devices. Data were collected at 28 VA medical centers with anticoagulation clinics that met guidelines defined by the Managing Anticoagulation Services Trial and were treating at least 400 patients.
Patients were followed for 2.0 to 4.75 years, for a total of 8,730 patient-years of follow up. Time to the first primary event was not significantly longer in the self-testing group (hazard ratio, 0.88; 95% confidence interval [CI], 0.75 to 1.04; P=0.14). Clinical outcomes were similar, except that the self-testing group reported more minor bleeding episodes. Also, the self-testing group had a 3.8% improvement in the percentage of time during which the INR was within the target range (95% CI, 2.7-5.0; P<0.001).
At two years, patient satisfaction with anticoagulation, as measured by the DASS (scores range from 25 to 225, with lower scores indicating better satisfaction) was greater in the self-testing group (−2.4 points; 95% CI, −3.9 to −1.0; P=0.002). The self-testing group also saw a cumulative gain in the Health Utilities Index Mark 3 (difference, 0.155 points; 95% CI, 0.111 to 0.198; P<0.001). Costs were higher in the self-testing group (difference, $1,249; 95% CI, -$1,205 to $3,703; P=0.32).
A limitation to the results is that the study criteria—a controlled setting, patients screened for competence and compliance with screening test manufacturers' guidelines—probably differ from real-life use.
Study authors wrote, “In light of the poor record of usual care and the value of anticoagulation in preventing major events, we recommend that self-testing be considered for patients whose access to high-quality anticoagulation care is limited by disability, geographic distance, or other factors, if the alternative would be to withhold a highly effective treatment.”