OBJECTIVES: Secondary hyperparathyroidism (sHPT), a common complication of end-stage kidney disease (ESKD), associates with mortality, cardiovascular events, fractures, and parathyroidectomy. Before 2018, over 20% of Medicare beneficiaries lacked access to calcimimetics, a class of medication used to treat sHPT, because they lacked Part D coverage. In 2018, a policy known as the Transitional Drug Add-On Payment Adjustment (TDAPA) transitioned coverage for calcimimetics in patients with FFS Medicare from Part D to Part B. We evaluated changes in filled calcimimetic prescriptions following TDAPA.

METHODS: We analyzed FFS Medicare claims from the United States Renal Data System from all adult patients in the U.S. who received at least 30 days of dialysis between 2015 and 2020 with FFS Medicare as the primary payer. The primary outcome was any filled calcimimetic prescription during a given month, and the primary exposure was monthly Part D coverage status (covered vs. not covered). In a difference-in-differences (DiD) model, we used two-way fixed effects linear regression with patient- and month-level fixed effects and an interaction term between the policy intervention (month occurring pre- vs. post-TDAPA) and Part D coverage status to estimate the policy effect of the TDAPA payment on calcimimetic prescriptions in individuals without Part D coverage.

RESULTS: Among 784,562 patients in our sample, 17,709,687 (80%) of patient-months had Part D coverage and 4,500,149 (20%) of patient-months did not. The DiD model demonstrated an 11.8% percentage point increase in filled calcimimetic prescriptions attributable to TDAPA in patients affected by the policy.

CONCLUSIONS: TDAPA increased prescriptions for calcimimetic agents in patients without Medicare Part D coverage, who were previously under-insured with respect to these medications. This finding illustrates that Medicare reimbursement policy has the potential to expand access and reduce healthcare disparities for patients receiving maintenance dialysis.