VOLUME 53 | NUMBER 4 | AUGUST 2018
Impact of CostSharing Increases on Continuity of Specialty Drug Use: A QuasiExperimental Study
Objective: To examine the impact of costsharing increases on continuity of specialty drug use in Medicare beneficiaries with multiple sclerosis (MS) or rheumatoid arthritis (RA).
Data Sources/Study Setting: Five percent Medicare claims data (2007–2010).
Study Design: Quasiexperimental study examining changes in specialty drug use among a group of Medicare Part D beneficiaries without lowincome subsidies (nonLIS) as they transitioned from a 5 percent costsharing preperiod to a ≥25 percent costsharing postperiod, as compared to changes among a diseasematched contemporaneous control group of patients eligible for full lowincome subsidies (LIS), who faced minor cost sharing (≤$6.30 copayment) in both the pre and postperiods.
Data Collection/Extraction Methods: Key variables were extracted from Medicare data.
Principal Findings: Relative to the LIS group, the nonLIS group had a greater increase in incidence of 30day continuous gaps in any Part D treatment from the lower costsharing period to the higher costsharing period (MS, absolute increase = 10.1 percent, OR = 1.61, 95% CI 1.19–2.17; RA, absolute increase = 21.9 percent, OR = 2.75, 95% CI 2.15–3.51). The increase in Part D treatment gaps was not offset by increased Part B specialty drug use.
Conclusions: Costsharing increases due to specialty tierlevel cost sharing were associated with interruptions in MS and RA specialty drug treatments.
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