Anticoagulation control and prediction of adverse events in patients with atrial fibrillation: a systematic review.
BACKGROUND Warfarin is recommended for prevention of stroke in patients with atrial fibrillation who are at moderate or high risk, but requires intensive management to achieve safe and optimal anticoagulation control. Anticoagulation clinics are often used to administer warfarin therapy more effectively. OBJECTIVE To collect data from multiple sites and assess the quality and costs associated with anticoagulation clinic services. METHODS A random sample of 600 adults with chronic nonvalvular atrial fibrillation (CNVAF) receiving warfarin was selected from anticoagulation clinics affiliated with 3 health plans. Patients were identified between 1996 and 1998 and followed for up to one year. We assessed the proportion of time that international normalized ratio (INR) values were within the recommended range (2.0-3.0) and the costs of anticoagulation clinic care. RESULTS Patients had an average of 18 clinic contacts over a mean duration of follow-up of 10.5 months. On average, patients were within the recommended INR range 62% of this time, with 25% of days below range and 13% above range. The mean per-patient cost of warfarin monitoring over the follow-up period averaged $261 at site A, $305 at site B, and $205 at site C (in 2003 US$). Mean costs for patients treated for one full year were $288, $339, and $216, respectively. CONCLUSIONS In 3 geographically diverse health plans, anticoagulation clinics provided a generally higher quality of control than previously reported in other observational studies. This study highlights the costs of obtaining this level of control.