Home INR testing for warfarin management

January 01, 0001

Home INR testing for warfarin management

As compared with venous plasma testing, point-of-care international normalized ratio INR measuring devices allow greater testing frequency and patient involvement and may improve clinical outcomes. These investigators from the US and Singapore randomly assigned 2922 patients who were taking warfarin because of mechanical heart valves or atrial fibrillation and who were competent in the use of point-of-care INR devices to either weekly self-testing at home or monthly high-quality testing in a clinic.

They found: "The patients were followed for 2.0 to 4.75 years, for a total of 8730 patient-years of follow-up. The time to the first primary event was not significantly longer in the self-testing group than in the clinic- testing group (hazard ratio, 0.88, not significant). The two groups had similar rates of clinical outcomes except that the self-testing group reported more minor bleeding episodes. Over the entire follow-up period, the self- testing group had a small but significant improvement in the percentage of time during which the INR was within the target range (absolute difference between groups, 3.8 percentage points; significant). At 2 years of follow-up, the self-testing group also had a small but significant improvement in patient satisfaction with anticoagulation therapy and quality of life."

The authors concluded: "As compared with monthly high-quality clinic testing, weekly self-testing did not delay the time to a first stroke, major bleeding episode, or death to the extent suggested by prior studies. These results do not support the superiority of self-testing over clinic testing in reducing the risk of stroke, major bleeding episode, and death among patients taking warfarin therapy."

The two approaches have roughly equivalent outcomes so the main difference is cost, which was not addressed in this report.

For the full abstract, click here.

N Engl J Med 363:1608-1620, 21 October 2010
© 2010 to the Massachusetts Medical Society
Effect of Home Testing of International Normalized Ratio on Clinical Events. David B. Matchar, Alan Jacobson, Rowena Dolor, et al. Correspondence to Dr. Matchar: david.matchar@duke-nus.edu.sg

Category: B. Blood/Blood Forming Organs/Immune Mechanisms, K. Circulatory. Keywords: warfarin, anticoagulation, international normalized ratio, INR, self-testing, point-of-care testing, randomized controlled trial, journal watch.
Synopsis edited by Dr Linda French, Toledo, Ohio. Posted on Global Family Doctor 16 November 2010

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