Calcimimetic Prescriptions in Fee-for-Service Medicare Beneficiaries Undergoing Dialysis.

Importance: Calcimimetics are a mainstay of treatment for secondary hyperparathyroidism (sHPT), a ubiquitous condition in end-stage kidney disease (ESKD) associated with fractures, cardiovascular events, and mortality. In 2018, Medicare implemented the Transitional Drug Add-On Payment Adjustment (TDAPA), which shifted calcimimetic coverage from Part D prescription drug plans to Part B. Prior to TDAPA, Medicare beneficiaries with ESKD faced varying out-of-pocket costs for calcimimetics at the point of pharmacy depending on presence and magnitude of low-income subsidies (LISs). TDAPA differentially alleviated barriers to filling these costly medications. Objective: To assess whether calcimimetic prescriptions increased post-TDAPA among patients subject to high out-of-pocket costs prior to the policy change (patients with Part D coverage without LIS and those lacking Part D coverage). Design, Setting, and Participants: In this longitudinal cohort study, a difference-in-differences analysis was performed at the patient-quarter level. The sample included adult Medicare fee-for-service beneficiaries undergoing maintenance dialysis between July 1, 2016, and December 31, 2020, at US outpatient dialysis facilities. The US Renal Data System, a national registry of patients with ESKD, was used to collect patient, facility, and claims data. The data analysis occurred between May 2023 and October 2024. Exposures: LIS extent for patients with Part D coverage (fully subsidized, partially subsidized, not subsidized); presence of Medicare Part D coverage; and whether the patient-quarter was before/after TDAPA implementation. Main Outcomes and Measures: The main outcome was having 1 or more filled calcimimetic prescriptions per quarter of the study period. A linear regression model was estimated, adjusting for demographics, dialysis modality and access, comorbidities, and facility characteristics, with 2-way fixed effects at the patient and quarter level. Results: A total of 509 765 adult Medicare fee-for-service beneficiaries were included in the analysis. The cohort had a mean (SD) age of 64 (14) years, was 57% male, 4% Asian, 38% Black, 15% Hispanic, 41% non-Hispanic White, and 3% other race and ethnicity. In adjusted difference-in-differences models, TDAPA's estimated effect was an absolute increase of 9.8 percentage points (pp) (95% CI, 9.3-10.2 pp) in calcimimetic prescriptions for patients with Part D but no subsidy and a 2.2 pp (95% CI, 1.8-2.6 pp) increase for patients with partial LIS compared to patients with full LIS. Conclusions and Relevance: The results of this longitudinal cohort study showed that after transitioning calcimimetic coverage from Part D to Part B via TDAPA, calcimimetic prescriptions increased in a graded manner, with the largest increases experienced by patients previously subject to the highest out-of-pocket prescription drug costs. Medicare's TDAPA policy has the potential to expand access to medications for patients.