From 2013 to 2016, Medicare Shared Savings Program accountable care organizations (ACOs) improved quality. Continued infrastructure development funding, better relationships with postacute care facilities, and shared learnings among diverse ACOs would maximize quality improvement.
Objectives: To investigate accountable care organization (ACO) quality improvement over the first 4 Medicare Shared Savings Program (MSSP) years.
Study Design: Fixed-effects analysis examined associations of within-ACO MSSP quality metric changes with key time-variant ACO traits: change in postacute care (PAC) expenditure and in size (attributed beneficiaries). Fixed-effects subgroup analyses and linear regression were used for key time-invariant traits: ACO taxonomy (physician-led, hospital-led, or co-led), risk-bearing maturity, commercial contract presence, and rurality.
Methods: The sources of data were secondary MSSP public use files linked to the Leavitt Partners ACO Database (ACO panel: n = 528; 2013-2016).
Results: Confirming early federal findings, MSSP ACOs, on average, improved most quality measures. Larger ACOs had higher quality, but ACOs grew rapidly for the first 3 years, bringing “growing pains” in quality measures related to clinical care for at-risk populations, before plateauing in size in the fourth year. By comparison, PAC expenditures increased in the first year but then decreased in all remaining years, and PAC spending changes were inversely associated with quality, especially in quality measures related to care coordination and patient safety. Successes and challenges varied most notably by ACO taxonomy, risk-bearing maturity, and rurality.