Background: High out-of-pocket costs for prescription medications have been associated with poor patient outcomes. A previous study found that the Part D coverage gap was significantly associated with decreases in adherence and persistence for medications frequently used in patients undergoing dialysis. It is not known what effect the decreased use of prescription drugs associated with the coverage gap had on utilization and spending for other medical care.
Objective: To determine the relationship between the Part D prescription drug cost-sharing structure and health and economic outcomes in Medicare beneficiaries on dialysis.
Methods: A retrospective analysis using data from the United States Renal Data System (2006-2008) was conducted for Medicare-eligible patients receiving dialysis. Patients were grouped in 1 of 4 cohorts based on low-income subsidy (LIS) receipt and benefit phase in 2007: Cohort 1 (non-LIS and did not reach the coverage gap); Cohort 2 (non-LIS and reached the coverage gap); Cohort 3 (non-LIS and reached catastrophic coverage after the gap); and Cohort 4 (received an LIS, and none of the LIS patients reached the coverage gap). Outcomes included medical care utilization, direct medical costs, and mortality.
Results: A total of 11,732 subjects met the inclusion criteria. Patients in Cohorts 1, 2, and 3 had $3,222 lower, $2,457 lower, and $1,182 higher adjusted pharmacy costs (P less than 0.001), but their adjusted hospitalization costs were $1,499 (P = 0.09), $2,287 (P = 0.01), and $2,959 (P = 0.01) higher, respectively, compared with Cohort 4 (LIS). In the propensity score-matched cohorts, patients who reached the coverage gap (Cohort 2) had higher rates of hospitalization (relative risk [RR] = 1.02, 95% CI = 0.94-1.10), outpatient visits (RR = 1.16, 95% CI = 1.08-1.25), and other visits (RR = 1.17, 95% CI = 1.03-1.32) compared with those who had an LIS (Cohort 4). Patients in Cohort 3 had a higher rate of outpatient visits compared with those in Cohort 4 (RR = 1.14, 95% CI = 1.03-1.25). There were no differences in medical care utilization between patients in Cohort 1 and Cohort 4. Compared with patients in Cohort 4 (LIS), patients in Cohort 2 (those who reached the coverage gap) had 9% higher hospitalization costs (RR = 1.09, 95% CI = 1.01-1.18) and 6% higher outpatient costs (RR = 1.06, 95% CI = 0.97-1.17), respectively. During the 1-year follow-up period, patients in Cohort 2 had a 20% (HR = 1.20, 95% CI = 1.05-1.37) and a 22% (HR = 1.22, 95% CI = 1.01-1.47) increased risk of all-cause and cardiovascular-related mortality compared with those in Cohort 4, respectively.
Conclusions: Our findings suggest that reaching the Part D coverage gap was associated with unfavorable clinical and economic outcomes in patients undergoing dialysis.