National Rates of Warfarin Use in Medicare Patients with Atrial Fibrillation: Results from the National Stroke Project
Background: The National Stroke Project is a HCFA initiative to improve stroke related hospital care for Medicare beneficiaries. As part of the evaluation of these efforts, HCFA is measuring performance on a set of quality indicators at the state and national levels. We report the baseline results for a key quality indicator for this project: warfarin at discharge for patients with atrial fibrillation (AF). Methods: Project data were abstracted from a national sample of Medicare inpatient charts with a principal or secondary diagnosis of AF (ICD-9-CM 427.31) and discharged between 4/98 and 3/99. All U.S. states, the District of Columbia, and Puerto Rico were sampled using a systematic random approach. Eligible patients were required to have physician confirmation of AF during the hospitalization and at discharge, or intermittent AF. The main outcome measure was a prescription or physician documented plan for warfarin at discharge. Results: Of 38,925 cases reviewed, 12,303 met the inclusion criteria. Many of the cases (38.3%) were excluded due to a history or current finding of hemorrhage. Nationwide, 6,633 (unadjusted rate, 53.9%) patients were prescribed warfarin at discharge or had a plan to start warfarin after discharge. The state-specific rates ranged from 30.7% to 65.3%. Univariate analyses showed that warfarin was prescribed less frequently (p<0.002) for adults 85 years of age and older (rate=39.9%, OR=0.47, 95% CI=0.43–0.51) and women (rate=52.0%, OR=0.83, 95% CI=0.78–0.90). African-Americans (rate=47.2%, OR=0.76 95% CI=0.63–0.90) and Asians (n=108, rate=37.0%, OR=0.50, 95% CI=0.34–0.74) were also found to have lower warfarin therapy rates. Conclusions: The results from this large national sample confirm the findings from other reports that there is substantial under-utilization of warfarin therapy for stroke prevention among Medicare patients with AF. This is particularly true for demographic subgroups at high risk for stroke. Quality improvement efforts are currently underway through HCFA’s National Stroke Project (AF topic) to increase warfarin use in appropriate AF patients.