Self-Monitoring of Anticoagulant Halves Thromboembolism Risk

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How Will This Help U.S. Patients?

The current meta-analysis confirms the findings from previous reports suggesting that in highly motivated patients, a strategy of self-directed care of anticoagulation improves the quality of anticoagulation, resulting in fewer thromboembolic events without increased risk of a serious bleeding event.

What are the implications for these findings, especially in the United States, where despite the use of home INR monitoring being reimbursed by the Centers for Medicare and Medicaid Services (for chronic oral anticoagulation management in patients with mechanical heart valves, chronic atrial fibrillation, or venous thromboembolism on warfarin), less than 1% of patients undertake self-testing at home?

First, these studies were highly selective in determining eligibility for home INR monitoring and management. About 50% or fewer of the screened patients participated in the self-care strategy; most patients older than 75, who are most likely to benefit from this strategy, were excluded; up to 25% withdrew after enrollment despite demonstrated improvements in quality of life. Thus, the findings only apply to those who are highly motivated, competent, and proficient in self-testing and self-titration.

Second, the populations studied were largely homogeneous, mostly from Europe (where the use of vitamin K antagonists other than warfarin is common), and included mostly white men. Only three studies were from the United States, the largest being THINRS (The Home INR Study) sponsored by the Department of Veteran Affairs and conducted mostly in Caucasian men (N. Engl. J. Med. 2010;363:1608-20). Thus, whether these results can be applied to a wider U.S. population across the spectrum of health care plans and where warfarin is the most commonly used vitamin K antagonist, remains to be determined.

Third, a major issue is cost. Although the present meta-analysis did not investigate cost, in THINRS the cost associated with self-testing was on average $1,249 more per year than usual care.

Finally, the approval and availability of newer anticoagulants such as dabigatran and rivaroxaban that do not require monitoring could potentially alter the landscape of home INR monitoring. However, because dabigatran and rivaroxaban have not been approved for anticoagulation therapy in patients with mechanical heart valves, a self-management strategy using vitamin K antagonists might still be the most desirable option for treating these patients.

Dr. Sanjay Kaul

Other considerations that might promote the continued use of warfarin in structured self-care programs for other indications include the expensive cost of the newer agents, familiarity of warfarin use in patients with renal insufficiency, and lack of a readily available antidote for reversal of anticoagulation with dabigatran and rivaroxaban.

Thus, several lingering issues remain about the general applicability of a self-care warfarin anticoagulation program in the United States. Whether this model is cost effective and can be implemented successfully in typical U.S. health care settings warrants further evaluation.

Sanjay Kaul, M.D., M.P.H., is a cardiologist at Cedars-Sinai Medical Center, Los Angeles. He disclosed that he owns stock in Johnson & Johnson.



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.

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