ResearchL ong-term oral anticoagulation therapy with vitamin K antagonists is prescribed as prophylaxis against strokes and other embolic events in patients with atrial fibrillation or a mechanical heart valve. 1,2 Warfarin therapy, however, is complicated by the variability of its biologic effect, its narrow therapeutic index, and the associated thrombotic or hemorrhagic events in the event of over-or underanticoagulation. 2 It has been shown that improved anticoagulant control can be achieved through frequent monitoring of the international normalized ratio (INR), resulting in improved health outcomes. 3 Monitoring the INR and managing warfarin dosing by a primary care physician is the current clinical standard of practice in Canada. 4 Physician management requires patients to visit a laboratory regularly for INR testing. The laboratory reports the INR to the physician, who subsequently contacts the patient with any required change in dosage. An alternative strategy is patient self-management. Self-management entails the measurement of the INR by the patient using a pointof-care device and, when necessary, self-adjustment of the warfarin dose using a nomogram. 4 Several published trials have compared self-management with physician management or management in an anticoagulation clinic. 4-13 It has been found that patients who self-manage check their INR more frequently and are able to maintain a greater proportion of INRs within the therapeutic range compared with those whose therapy is monitored by a physician or in an anticoagulation clinic. [11][12][13] The results of a recent meta-analysis showed a significant reduction in thromboembolic events (odds ratio [OR] 0.45), major hemorrhagic events (OR 0.65) and all-cause mortality (OR 0.61) for those using a self-management or self-test strategy. 14 The results also showed that self-management compared with self-testing alone reduces the occurrence of thromboembolic events (OR 0.27) and death (OR 0.37). 14 These results, together with the greater initial costs of educating patients to self-manage and of the pointof-care device itself, provide the impetus for a formal costeffectiveness analysis.The objective of this study was to evaluate the incremental cost and health benefits of self-managed versus physicianmanaged chronic oral anticoagulation therapy from the perspective of the Canadian health care payer. A Bayesian approach was adopted to facilitate the incorporation of prior knowledge of transition probabilities and for probabilistic sensitivity analysis. Cost-effectiveness of self-managed versus physician-managed oral anticoagulation therapy Background: Patient self-management of long-term oral anticoagulation therapy is an effective strategy in a number of clinical situations, but it is currently not a funded option in the Canadian health care system. We sought to compare the incremental cost and health benefits of self-management with those of physician management from the perspective of the Canadian health care payer over a 5-year period.