National assessment of Medicare prescription plan coverage gaps among patients with atrial fibrillation in the US.

INTRODUCTION: The Medicare Part D prescription plan has a coverage gap from $2250 to $5100 per year (2006 thresholds) in which patients pay full drug costs (the "donut hole"). We examined prescription costs in patients aged >or=65 years with atrial fibrillation (AF), and the proportions entering/exiting the donut hole in 2006.

METHODS: This retrospective cohort study used claims data from the Integrated Healthcare Information Systems National Managed Care Benchmark Database from January 2005 to December 2006. Medicare Advantage patients aged >or=65 years who were hospitalized with a primary/secondary discharge diagnosis of AF, or had >or=2 outpatient AF claims without hospitalization in 2005, were identified. Total 2006 prescription costs were calculated by summing health plan payments and patient copayments.

RESULTS: Of 16,655 patients included in the analysis, 1527 were hospitalized with a primary AF diagnosis, 6067 with a secondary AF diagnosis, and 9061 had outpatient-managed AF in 2005. Mean 2006 per-patient prescription costs were $3457.16. In total, 58.8% of patients reached the $2250 threshold in a mean of 199 days; including 59.9% of primary AF hospitalization, 63.5% of secondary AF hospitalization, and 55.5% of patients with outpatient-managed AF. Of the overall population, 21.2% reached the $5100 threshold in a mean of 257 days; including 21.3% of primary AF hospitalization, 27.3% of secondary AF hospitalization, and 17.2% of patients with outpatient-managed AF. AF-related drugs accounted for only 15% of the total prescription costs, with the majority of costs relating to the treatment of non-AF comorbidities.

CONCLUSIONS: In 2006, total annual prescription costs in this population of Medicare Advantage AF patients were considerable. In this sample population, over half of patients would have had prescription costs in excess of the 2006 Part D donut hole threshold. The costs of AF treatment itself were relatively low, with the majority of prescription costs relating to the treatment of non-AF comorbidities.