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Optimal Warfarin Management for Prevention of Thromboembolic Events in Patients with Atrial Fibrillation [Internet]. Ottawa (ON): Canadian Agency for Drugs and Technologies in Health; 2011 Nov. (CADTH Optimal Use Report, No. 1.2.)

Cover of Optimal Warfarin Management for Prevention of Thromboembolic Events in Patients with Atrial Fibrillation

Optimal Warfarin Management for Prevention of Thromboembolic Events in Patients with Atrial Fibrillation [Internet].

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7.1. Summary of Evidence

Patient self-management was reported to have an ICER of $14,000 per QALY, compared with physician-managed anticoagulation, from a health payer perspective over a five-year time horizon.13 The model estimated that self-management prevents 3.5 major thrombotic and 0.8 major hemorrhagic events per 100 patients over five years. The ICER of self-management was $237,000 in the first year of therapy due to the resources involved in training patients, which were not offset by a substantial reduction in warfarin-related complications or thromboembolic events. The cost-effectiveness of self-management improves if patients continue with this type of management for more than one year. Confidence in the ICER values depends on the strength of the clinical data used to populate the model, which in this study13 may be considered less robust.

A costing study (Schulman et al.15) reported that hospital-based physician- or pharmacist-managed anticoagulation was associated with lower three-month costs than community physician-managed care, from the health payer or societal perspective. In contrast, Lalonde et al.14 reported that pharmacist-managed anticoagulation services were associated with incremental annual costs of $124 per patient compared with family physician-managed care. The differences in the findings of these two studies may be explained, in part, by the costing methods used and the patient population studied. In the Lalonde study,14 approximately 90% of patients were new users of warfarin, compared with 32% of patients in the Schulman15 report. In Schulman et al.’s study,15 patients attending hospital-based clinics were younger, used fewer chronic medications, and were less likely to have atrial fibrillation than those treated by community physicians. The Lalonde study14 used simple costing methods that may not have captured all relevant costs of care. A third costing study (Bungard et al.16) reported cost savings due to reduced hospital and ER visits among patients referred to a pharmacist-managed anticoagulation clinic. This study, however, had methodological issues that may limit the validity of the findings.

7.2. Limitations

Overall, the data on costs of specialized anticoagulation services in Canada were limited. Four studies met the inclusion criteria, including one cost-utility study13 and three costing studies.1416 All studies included a mixed population and did not provide cost data specific to patients with atrial fibrillation.

Two costing studies were based on up to six months of follow-up of patients, which was insufficient to capture differences between comparators on the costs and health resources related to clinical outcomes such as bleeding or thromboembolic events.14,15 Lack of a concurrent control group, selection bias, and an analysis restricted to hospitalization and ER visit costs limited the validity of the before and after study.16

The cost-utility analysis13 was based on clinical outcomes extrapolated from a single RCT reporting surrogate outcomes, and therefore the cost-effectiveness estimates should be interpreted with caution.

Copyright © 2011 CADTH.
Bookshelf ID: NBK169510
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