NEW ORLEANS — Patients taking warfarin who regularly self-tested their level of anticoagulation at home had outcomes that were at least as good as, and in some cases better than, patients who were monitored by regular monthly visits to an anticoagulation clinic.
This good performance by patient self-testing of their international normalized ratio (INR) suggests that “home self-testing is an acceptable alternative to high-quality clinic care and may be preferable when patient access [to a clinic] is difficult,” Dr. Alan K. Jacobson said at the annual scientific sessions of the American Heart Association.
Expanded home INR monitoring could “lead to an improvement in quality, particularly with an appropriate infrastructure. I'm hopeful this will be an option for a lot of patients,” Dr. Alan S. Go, assistant director for clinical research for Kaiser Permanente of Northern California in Oakland, said in an interview.
Home monitoring of INR levels may now be particularly attractive for insurers and physicians because Medicare began last March to allow reimbursement for home monitoring of patients with atrial fibrillation or venous thromboembolism, noted Dr. Go, who was not involved with the study.
“Patients in the self-testing group had a higher rate of time in their target INR range, and they liked using the [home-monitoring] device,” said Dr. David B. Matchar, director of the Duke Center for Clinical Health Policy Research in Durham, N.C., and cochair of the study. The results show that “home testing provides another option for high-quality anticoagulation.”
The Home INR Study (THINRS) was run at 28 Veterans Affairs medical centers, each of which had an anticoagulation clinic that met the 2002 guidelines of the Managing Anticoagulation Services Trial (Am. J. Med. 2002;113:42–51). The study used the ProTime device and system made by International Technidyne Corp. The INR-measuring devices and kits used in the study were purchased by the VA through the federal bid process, and the study received no commercial support, said Dr. Jacobson, who disclosed that he has received research support (for other studies) from International Technidyne and several other manufacturers of INR measurement devices. Dr. Matchar said that he had no financial relationships to disclose.
The study initially enrolled 3,644 patients who required warfarin treatment because of either atrial fibrillation or a mechanical heart valve. Patients received training in using the home monitor, which took about 30 minutes, and then used the device at home for 2–4 weeks. They then returned to their local center for an assessment of how well they had monitored their INR level, either completely on their own or with the assistance of a caregiver at home.
Of the initial 3,644 patients, more than 700 patients dropped out, failed training, or failed to adequately monitor themselves, but 2,922 patients (80% of the original group) demonstrated that they could successfully handle home monitoring and progressed to the randomized part of the study. Their average age was 67 years, with a range of 23–99. About two-thirds of the patients had atrial fibrillation.
The patients were randomized to either continue weekly INR self-testing at home or come to the clinic for monthly INR testing (control group). The at-home patients called in their test results each week and if necessary were given instructions by telephone for dosage adjustment. Home-monitored patients were seen in the clinic when required by changes in their status. Patients remained on their monitoring schedules for 2–5 years.
The study's primary end point was the combined rate of stroke, major bleeding, or death during the study. This rate was 8.9% in the control patients and 7.9% in the self-monitored patients, a difference that was not statistically significant but did show that home monitoring was not harming patients, said Dr. Jacobson, a cardiologist and associate chief of staff for research at the Loma Linda (Calif.) VA Medical Center.
A secondary end point was the time each patient spent within their INR therapeutic range. The average rate was 62% in the control patients and 67% in the home-monitored patients, a statistically significant difference.
A related interview with Dr. Matchar can be seen at www.youtube.com/InternalMedicineNews