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Well-monitored anticoagulation with warfarin potentially could prevent more than half of the strokes related to atrial fibrillation (rapid, irregular heart beat) with a relatively low risk of major bleeding complications. Although the therapy is widely recommended, many patients with atrial fibrillation either do not receive warfarin or are not maintained within an optimal coagulation range. For most patients, the international normalized ratio (INR) suggests a prothrombin time of 2-3 minutes, which can be difficult to achieve consistently in the setting of a busy community practice.
In a recent study, supported in part by the Agency for Healthcare Research and Quality (contract 290-91-0028), investigators examined the impact on patients with atrial fibrillation of the availability of an anticoagulation service developed in a managed care organization (MCO). David Matchar, M.D., of Duke University, and members of the Stroke Prevention Patient Outcomes Research Team (PORT) compared the outcomes of MCO patients 65 years and older who either had access to an anticoagulation service or received usual care.
Six large managed care sites in the United States participated in the trial, and five of these were able to establish and maintain an anticoagulation service that met the functional specifications for the study. Control practices within each managed care site continued their usual provider-based care.
The primary outcome measure was time in target range—that is, the number of days for which the INR was between 2 and 3. Secondary outcomes measures were thromboembolic events and major bleeding. Data were collected by chart for audit for the 9 months prior to the onset of the anticoagulation service and, following service initiation that varied from 6 to 14 months, for a period of 9 months after the service had attained maximum enrollment.
The results indicate that a properly administered anticoagulation service can successfully manage the anticoagulation of most patients with atrial fibrillation. However, the services at the five sites in the study did not significantly improve anticoagulation relative to usual care at these sites. Percentage of time in the INR target range was similar for the 144 patients in the intervention group (baseline 48 percent; followup 56 percent) and the 118 patients in the control clusters (baseline 49 percent; followup 52 percent).
The researchers conclude that the effect of the anticoagulation service was limited by the use of the service, the degree to which referring physicians supported strict adherence to recommended target ranges for the INR, and the ability of the anticoagulation service to identify and respond promptly to out-of-range values.
See "Improving the quality of anticoagulation of patients with atrial fibrillation in managed care organizations: Results of Managing the Anticoagulation Services Trial," by Dr. Matchar, Gregory P. Samsa, Ph.D., Stuart J. Cohen, Ed.D., and others in the July 2002 American Journal of Medicine 113, pp. 42-51.
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