Objectives: To determine the per-patient-per-month (PPPM) cost of a decentralized outpatient pharmacy anticoagulation service (OPAS) in patients with chronic atrial fibrillation (AF) who were maintained on warfarin sodium therapy in a managed care setting, to compare the annual costs versus the risk for stroke, and to assess the quality of the anticoagulant management.
Methods: Data were collected retrospectively from clinical, research, and administrative claims databases. Patient demographic data were stratified to include age and risk factors for stroke. Inclusion criteria for the study were adult patients (>18 years) who were maintained on chronic warfarin therapy with a diagnosis of AF (diagnosis code 427.31) and continuously enrolled during calendar year 2000. The cost analysis included the personnel cost of clinical pharmacy specialists, direct and indirect cost of laboratory tests for international normalized ratios (INR), and anticoagulant (warfarin plus bridge therapy with a low molecular weight heparin) drug cost and dispensing fee. The percentage of INR values within or near target was used to evaluate the effectiveness of the service.
Results: A total of 97 patients on chronic warfarin therapy for AF were identified for cost analysis. The demographics for these patients included the following: 71% were male, with 32% of the patients over the age of 75 years, and 60% had 1 or more identifiable risk factors for stroke. Utilizing established criteria, 80.4% of the sample was considered to be at high risk for ischemic stroke. A majority of the patients (94.8%) had nonvalvular disease, with an INR goal in the range of 2 to 3 in 91.8% of the cases. The PPPM cost for the OPAS monitoring service was $51.25, distributed as $13.78 (27%) in personnel costs for monitoring pharmacists, $18.38 (36%) for lab tests, and $19.09 (37%) for anticoagulant drug costs. These costs did not significantly differ among patient groups with various risks for ischemic stroke. For nonvalvular AF patients, the percentage of INR values within each individual patient.s specific INR goal range was 60.4%; the percentage within or near goal was 74.6%.
Conclusion: The average PPPM cost for pharmacist and laboratory monitoring as well as anticoagulant medication for CY 2000 was estimated to be $51.25. The annual costs were comparable among AF patients with different risks for ischemic stroke. The percentage of INR values within the individual patient.s stated target goal was 60.4%. Effective monitoring to maintain patients within their target INR goal is relatively inexpensive compared with the cost of complications such as ischemic stroke or intracranial bleeding.