Project Summary / Abstract Up to 80% of patients with end-stage kidney disease (ESKD) receiving dialysis have secondary hyperparathyroidism (SHPT), a condition of abnormal bone and mineral metabolism which is associated with higher mortality, cardiovascular events, fractures, and parathyroidectomy. Calcimimetics, a mainstay of treatment for SHPT, act by lowering parathyroid hormone (PTH) secretion; cinacalcet and etelcalcetide are the two FDA-approved calcimimetics available in the United States. Before 2018, over 20% of Medicare beneficiaries lacked access to these medications because they lack Medicare Part D (prescription drug coverage). In 2018, all dialysis patients suddenly gained access through a change in Medicare policy known as the Transitional Drug Add-On Payment Adjustment (TDAPA). Using administrative claims data from the United States Renal Data System (USRDS), which houses Medicare claims for all individuals on dialysis, this project will leverage the TDAPA policy as a natural experiment to evaluate its effect on calcimimetic prescriptions and subsequent patient morbidity and mortality. Aim 1 seeks to compare the prescribing patterns of calcimimetics for individuals on dialysis before and during TDAPA, using a longitudinal differences-in-differences analysis to estimate the effect of the TDAPA policy in patients without Medicare Part D coverage. Early studies of TDAPA suggest that calcimimetic prescription patterns varied widely from facility to facility. Sub-Aim 1a will study differences between cinacalcet and etelcalcetide use after implementation of TDAPA, focusing on comparing the facility characteristics associated with greater likelihood of etelcalcetide use. Aim 2 attempts to evaluate SHPT-associated outcomes and determine whether expanded access to calcimimetics ameliorated poor outcomes through a differences-in-differences analysis of TDAPA. Though SHPT is associated with morbidity and mortality, whether calcimimetics can improve such outcomes is less clear, owing to limitations of randomized-controlled trials. In this aim, the TDAPA policy will be used as a natural experiment to examine the causal, real-world effect of calcimimetics on SHPT-associated outcomes, with broader implications for examining how Medicare policies affect important outcomes for patients on dialysis. The proposed work will serve as a post-doctoral fellowship training vehicle for the applicant at Stanford University, under an interdisciplinary mentorship team bridging Stanford’s Division of Nephrology and Department of Health Policy, with collaboration from the University of Southern California. This team brings expertise in bone mineral disease, USRDS data, and econometrics that will equip the trainee with the necessary skills to advance her career in health services research with a focus on the ESKD population.