Home prothrombin time monitoring after the initiation of warfarin therapy. A randomized, prospective study

Abstract

Study objective: To evaluate the efficacy and accuracy of monitoring prothrombin times at home.

Design: Randomized, prospective cohort study.

Setting: Outpatients discharged from a university hospital or a community hospital.

Patients: Fifty patients started on warfarin for the first time who demonstrated an ability to use the monitor and who had not achieved a stable response to warfarin in the hospital.

Intervention: Oral anticoagulation therapy managed using a portable prothrombin time monitor compared with specialized anticoagulation clinic care.

Measurements and main results: In the 46 patients who completed the 8-week study, the median percentage of time that patients in the home-monitor group (n = 23) were within a range equal to the target prothrombin ratio +/- 0.3, but always above 1.25, was 93%, compared with 75% for patients in the clinic group (n = 23) (P = 0.003). There was no significant difference between groups in the percentage of time above the therapeutic range; however, the percentage of time that patients were subtherapeutic was significantly greater in the clinic group (P less than 0.001). There were no major thromboembolic or hemorrhagic complications in either group. Differences between home monitor measurements and corresponding clinical laboratory measurements using blood samples drawn within 4 hours of the home test were comparable to differences observed between measurements using two different clinical laboratory instruments.

Conclusions: Use of a portable prothrombin time monitor by patients at home is feasible and provides accurate measurements. Patients doing home monitoring achieve superior anticoagulation control compared with those receiving standard anticoagulation clinic care.