Do anticoagulation management services improve care? Implications of the Managing Anticoagulation Services Trial

An Anticoagulation Clinic Service (ACS) has been proposed as one strategy for improving warfarin treatment for patients with atrial fibrillation. In the Managing Anticoagulation Services Trial (MAST), ACSs meeting specifications for high quality care were established in six managed care organizations (MCOs) which had the patients and resources to support this initiative. The trial followed 1165 patients age >or=65 years who had atrial fibrillation as the primary reason for anticoagulation and were enrolled in a participating MCO. The 593 patients in the intervention group saw physicians in a practice cluster which had randomly been assigned to have access to an ACS. These physicians used the ACS on average for about 48% of eligible patients. The 572 patients in the control group received care from physicians in a practice cluster which could not refer patients to the ACS established for the trial but was otherwise unrestricted. The two clusters were compared on the proportion of time warfarin-treated patients were in the target range (2-3) prothrombin time-international normalized ratio (INR) during a 9-month baseline and a 9-month follow-up period. Among patients ( n = 264) for whom data were available for both periods, the changes in percentages of time in the target range were similar in the intervention cluster (baseline: 47.7%; follow-up 55.6%) and in the control cluster (baseline: 49.1%; follow-up: 52.3%; intervention effect: 5%; 95% confidence interval: -5% to 14%; P = 0.32). In both practice clusters, patients had subtherapeutic INR values (1.5 to 1.99) about one fourth of the time. Providing an ACS in a managed care setting did not appear to improve anticoagulation care over the usual care provided at the sites in this trial but could be a reasonable consideration in a practice setting where time in target range is less than 50%. A higher rate of utilization and a more aggressive stance toward subtherapeutic INR values could potentially enhance the effectiveness of an ACS.