Comparing patient OOP spending for specialty drugs in Medicare Part D and employer-sponsored insurance

Per capita spending on specialty drugs increased 55% between 2014 and 2018. Individuals aged 55 to 75 years using specialty drugs make the transition from employer-sponsored insurance (ESI) to Medicare Part D coverage. We compared out-of-pocket (OOP) spending across ESI, Medicare fee-for-service (FFS), and Medicare Advantage (MA) prescription drug plans to examine the impact of benefit design on OOP spending.

Analyses consisted of Truven MarketScan and Medicare Part D prescription drug claims from 2013 to 2017 for individuals enrolled in ESI, FFS, and MA drug plans taking at least 1 drug among the top 4 specialty drug classes: rheumatoid arthritis (RA), multiple sclerosis (MS), cancer, and hepatitis C.

Multivariate regression analyses with fixed effects were used to assess whether there are differences in OOP spending by insurance type and the impact of benefit design differences. A secondary outcome was drug choice within a therapeutic class.

There were small differences in drug choice between Medicare and ESI but significant differences in OOP spending. Monthly OOP spending for ESI relative to FFS was $108 less for RA drugs, $288 less for MS drugs, $504 less for cancer drugs, and $1437 less for hepatitis C drugs. Spending was slightly greater for beneficiaries in MA plans compared with FFS. Higher Medicare spending was driven by gaps in coverage in the Part D benefit phases because beneficiaries pay a percentage of list price.

OOP spending was substantially higher for Medicare enrollees compared with ESI enrollees as a result of the Part D benefit structure.