December 1st, 2011

Meta-Analysis Finds Benefits for Self-Monitoring in Some Warfarin Patients

Despite the advent of newer anticoagulants that don’t require monitoring, millions of people will continue to take warfarin for many years to come. Now a new meta-analysis published in the Lancet suggests that some of these patients may benefit from self-monitoring.

Carl Heneghan and colleagues analyzed data from 11 trials with 6417 patients on oral anticoagulation and 12,800 person-years of follow-up. They found a significant reduction in thromboembolic events among self-monitoring patients, but no reductions in major hemorrhagic events or death. Patients who were younger than age 55 and those with mechanical heart valves had large reductions in thrombotic events with self-monitoring.

Hazard ratios and 95% confidence intervals for the self-monitoring group and subsets were:

  • Thromboembolic events: HR 0·51, 0·31–0·85
  • Major hemorrhagic events HR 0·88, 0·74–1·06
  • Death: HR 0·82, 0·62–1·09
  • Thrombotic events in patients <55 years: HR 0·33, 0·17–0·66
  • Thrombotic events in patients with mechanical heart valve: HR 0·52, 0·35–0·77).

The authors calculated that 21 patients under the age of 55 would need to self-monitor for 1 year to prevent one thromboembolic event. For mechanical valve patients, the NNT was 55.

In an accompanying comment, Paul Alexander Kyrle and Sabine Eichinger write that self-monitoring should “be offered to patients with mechanical heart valves, especially those younger than 55 years. However, we do not see a place for self-monitoring in other areas of this treatment except for individual patients for whom access to routine usual anticoagulation care is restricted.”

4 Responses to “Meta-Analysis Finds Benefits for Self-Monitoring in Some Warfarin Patients”

  1. David Powell , MD, FACC says:

    I believe “studies” like this (or more accurately data manipulation) are fraught with selection bias, confounding findings irreparably.

  2. david, i think i agree, but you are terse. the terms self monitoring, self testing and self management have in common the word self, but seem like 3 separate entities with differing problems of implementation, risk and reimbursement. as mentioned, this is very uncommon in the usa, probably because of fee for service structure with multiple type of reimbursement and insurers. simple explanation is that no one has more skin in the game than the patients themselves and when they exercise that option that they are their own best advocates their well-being is enhanced.

    Competing interests pertaining specifically to this post, comment, or both:

  3. I am a measurement and monitoring advocate. However, perhaps more “skin in the game” can explain the conclusion that some patients are astute enough to be their best advocates in this particular analysis, but in most health issues in which there is choice, patients do not necessarily act in their own interest.

    The prevalence of poor adherence (over 50%), unhealthy lifestyle (well over 80%) and common improper choice and use of OTC medications–appropriateness and dosage–bespeak of a wide chasm between announced or assumed patient self-advocacy and improved outcomes due to actual consistent, healthy behavior.

    Richard Kones MD

  4. Highly selected patients will manage this fine, but in an usual patient population I guess we can count on the common 50 % adherence.

    Competing interests pertaining specifically to this post, comment, or both: