Participation in the Medicare Shared Savings Program (MSSP) was not associated with improvements in spending, quality of care, or outcomes. Selection effects – including exit of high-cost clinicians – may contribute to overstated estimates of savings. Findings from an instrumental variable analysis are published in Annals of Internal Medicine.
The MSSP is a program where groups of clinicians, hospitals and other providers voluntarily assume responsibility for the spending and quality outcomes of a defined population of free-for-service Medicare beneficiaries.
Accountable care organizations (ACOs) in the MSSP are associated with modest improvements in spending and quality. However, estimates of these savings may be overstated if high-cost physicians exit the program.
Researchers from the University of Michigan School of Public Health used national Medicare data to evaluate changes in spending and quality performance while accounting for selection effects in the MSSP. The authors used adjusted longitudinal models that accounted for secular trends, market-level factors, and observed differences across MSSP participants and local control beneficiaries.
To account for clinicians’ nonrandom entry and exit from the MSSP, the number of nearby clinicians in the MSSP was used as an instrumental variable. Hip fracture served as the falsification outcome.
The researchers found that participation in MSSP was not associated with improvements in spending, quality, or hip fracture (the falsification outcome). Before the start of the MSSP, spending trends differed between beneficiaries who did and did not enter the program.
Supplemental analyses found that high-cost clinicians and beneficiaries were disproportionately likely to exit MSSP ACOs, suggesting that improved quality and spending performance in MSSP may have been driven by nonrandom exit of clinicians and their patients.