Patients who self-monitor their anticoagulation therapy with warfarin reduce their risk of thromboembolic events by half, compared with those in conventional care, U.K. researchers have found.
The researchers, who analyzed individual patient data from 11 randomized controlled trials, saw the benefit as especially marked in patients under age 55, and in those with mechanical heart valves. The types of self-monitoring interventions differed between the studies, and self-management, in which both testing and titration are carried out by the patient, was seen as considerably more helpful than self-testing alone (in which a physician adjusts the dose).
Also, in contrast to findings from a recent meta-analysis (Ann. Intern. Med. 2011;154:472-82), no significant mortality benefit was seen for self-monitoring, compared with conventional care. The risk of major hemorrhage was not significantly reduced in the self-monitoring groups. And while people with atrial fibrillation saw a reduction in thrombosis risk of up to a third, this difference did not reach statistical significance because of the small number of events.
For their research, published online Nov. 30 in the Lancet (doi: 10.1016/S0140- 6736(11)61294-4), Dr. Carl Heneghan, of the department of primary care health sciences at Oxford (U.K.) University, and his colleagues identified 11 randomized controlled trials comparing self-monitoring interventions (8 of which involved self-management) with conventional care for which individual patient data were available. A total of 6,417 patients were included in their analysis, 22% of them women.
Dr. Heneghan and his colleagues looked at time to death, first major hemorrhage, and first thromboembolic event among patients self-monitoring or under conventional care with warfarin and other vitamin K antagonists. Overall, the self-monitoring group saw a significant reduction in thromboembolic events (hazard ratio, 0.51) but not in major hemorrhage or death.
People under age 55 showed a risk reduction of two-thirds for thromboembolic events (HR, 0.33), and in patients with mechanical valves the risk was about halved (0.52).
Patients in the studies evaluating self-management interventions saw greater risk reduction over conventional care (HR, 0.42) than did those in the studies evaluating self-testing alone (0.74).
In subjects aged 85 years and older (n = 99), there were no significant adverse effects of the intervention for all outcomes, which suggested, Dr. Heneghan and his colleagues wrote, that self-monitoring was a "safe option for suitable patients of all ages."
Dr. Heneghan and colleagues’ study was funded by the U.K. National Institute for Health Research. While neither Dr. Heneghan nor his coauthors disclosed conflicts of interest related to their findings, various relationships were disclosed by the investigators of the original trials whose data were used for the meta-analysis.
In an editorial comment accompanying Dr. Heneghan and colleagues’ study, Dr. Paul Alexander Kyrle and Dr. Sabine Eichinger, of the Medical University of Vienna, wrote that the study results do not support the broader use of self-monitoring, but rather support self-monitoring only in patients with mechanical heart valves, particularly those under age 55.
The good results in these patients, they wrote, may be because they are "highly aware of thromboembolic risks and are therefore prepared to manage their medical treatments, including therapy with vitamin K antagonists."
For patients with atrial fibrillation, who were not shown to benefit significantly in Dr. Heneghan and colleagues’ analysis, self-monitoring of vitamin K antagonists could soon become unnecessary with the introduction of newer anticoagulants that do not require monitoring and, in some cases, may be superior in reducing stroke and bleeding in patients with atrial fibrillation, Dr. Kyrle and Dr. Eichinger wrote.
Dr. Kyrle and Dr. Eichinger disclosed that they are consultants for Bayer, the manufacturer of rivaroxaban.