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INR self-monitoring and oral anticoagulants

FEATURED REVIEW It appears that oral anticoagulant therapy can be optimised by INR measurement at least every two weeks, with immediate dose adjustment. INR self-measurement can help to ensure that these conditions are respected.
Full review (3p) in English available for download by subscribers.

Abstract

  • The international normalised ratio (INR) must be measured regularly in order to maximise the benefits and minimise the risks of oral anticoagulant therapy. Devices are now available for INR measurement at home, by the patient or a caregiver. We examined whether these devices help to prevent bleeding or thromboembolism by reviewing the relevant literature using the standard Prescrire methodology.
     
  • INR self-measurement is reproducible and consistent with values obtained in medical laboratories.
     
  • Three meta-analyses of randomised trials show that a strategy based on patient training, INR self-measurement and, in most trials, dose adjustment by the patient or a caregiver reduces overall mortality and the number of thromboembolic events compared with conventional laboratory monitoring. In contrast, there was no impact on the frequency of serious bleeding. The INR was measured once every one or two weeks in the self-measurement groups.
     
  • This benefit probably resulted from a combination of several factors, such as better patient awareness of the importance of regular INR measurement, easier access to INR measurement, more rapid treatment adjustment, and more frequent INR measurement.
     
  • It remains to be seen whether a similar benefit will be observed in France, a country with a dense network of medical laboratories.
     
  • It is essential for patients to be trained in the self-measurement technique and, if necessary, to interpret the results and adjust the dose regimen. Depending on the trial, between 10% and 95% of eligible patients agreed to be trained in self-measurement and to adopt it in practice. However, in a British trial only half of the patients who agreed to be trained were actually capable of INR self-measurement and dose adjustment for at least one year.
     
  • In practice, it appears that oral anticoagulant therapy can be optimised by INR measurement at least every two weeks, with immediate dose adjustment, whether the INR is measured in a laboratory or by the patients at home. INR self-measurement can help to ensure that these conditions are respected.

©Prescrire July 2010

Source: Prescrire International 2010; 19 (107): 130-132 (pdf, subscribers only).
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