ArticlesSelf-monitoring of oral anticoagulation: a systematic review and meta-analysis
Introduction
Oral anticoagulation with vitamin K antagonists clearly reduces thromboembolic events.1, 2, 3, 4, 5, 6 In particular, well-controlled anticoagulation with warfarin could potentially prevent more than half the strokes related to atrial fibrillation and to heart-valve replacements, with a low risk of major bleeding complications.7 However, much of this potential benefit is still not realised because anticoagulation is either not done or not done well.
The therapeutic range for anticoagulants is narrow: an international normalised ratio (INR) of less than 2 increases the risk of thromboembolism, and an INR of more than 4·5 increases the risk of major bleeding.8, 9, 10 To maintain the INR within this narrow target range requires frequent testing and appropriate adjustment. When monitored monthly, around 50% of patients remain within target range,11 compared with 85% when monitored weekly.12 Numerous barriers to the use of warfarin exist, including the complex pharmacokinetics of warfarin, the need for continuous monitoring and dose adjustments, bleeding events, non-compliance, drug interactions, and increased costs of monitoring and therapy.7
One way to improve anticoagulation management is the use of home testing devices that allow the patient to measure INR with a drop of whole blood.13 Such hand-held devices have proved sufficiently reliable.14, 15 When self-monitoring, the patient can either self-test and self-adjust treatment according to a predetermined dose-schedule, or self-test and call a clinic to receive the appropriate dose adjustment. Potential advantages of self-monitoring include improved convenience for patients, better treatment compliance, more frequent monitoring, and fewer thromboembolic and haemorrhagic complications.16 Self-monitoring of anticoagulation seems a credible alternative to existing models of care, although published guidelines state that there are no reliable clinical-outcome data in any of the published studies to lend support to its use.17
We aimed to assess the current evidence for the effectiveness of self-monitoring and self-adjustment by patients on treatment with oral anticoagulation.
Section snippets
Eligibility and search strategy
We included all published and unpublished controlled trials that: randomly assigned patients; compared the effects of self-monitoring (self-testing) or self-management (self-testing and self-dosage) of anticoagulation with control and dosage by personal physician, anticoagulation management clinics, or managed services; or reported the clinical outcomes of thromboembolic events and major bleeding episodes. We included studies of adults and children on anticoagulant therapy irrespective of the
Results
We identified 345 citations (figure 1). Of these, two authors screened 254 abstracts and identified potentially relevant studies (91 duplicate records were excluded). We independently reviewed 31 retrieved articles for inclusion criteria and data extraction. The reviewers were not masked to any aspect of the studies (eg, journal type, author names, or institution). A total of 14 articles met the eligibility criteria.
There were 14 randomised trials with a total of 3049 participants compared
Discussion
Although no trial alone was significant, the combined trials suggest that self-monitoring of oral anticoagulation leads to a significant one-third reduction in death from all causes. Both benefits and harms of anticoagulation seem to be improved by self-monitoring: thromboembolism was decreased by 55%, and major haemorrhage was also decreased. In those who also self-adjusted therapy, there seemed to be a greater reduction in thromboembolic events and mortality than self-monitoring alone, but at
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