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Access Type

Open Access Thesis

Document Type


Degree Program

Public Health

Degree Type

Master of Science (M.S.)

Year Degree Awarded


Month Degree Awarded




While value-based payment models emphasizing care coordination have been widely implemented to improve quality and lower expenditures, supporting empirical evidence is sparse. Our objective was to quantify the impact of specialist-to-primary care physician involvement within accountable care organization (ACO) and its association with lower spending.


We conducted a retrospective cohort study of Medicare Shared Savings Program ACOs from 2012-2016 using publicly available data provided by the Centers for Medicare and Medicaid Services at the ACO level. We examined the association between the proportion of primary care services delivered by specialists versus other types of care providers and ACO spending using a generalized estimating equation model.


The analytic dataset included 1381 MSSP-years. When compared to ACOs at the lowest (60) levels of providing primary care services through specialists, ACOs who had 35% to 40% of primary care services delivered by specialists spent $1,124 (95% CI, $358 to $1,891) and $969 (95% CI, $250 to $1,688) less per capita, respectively. When stratified at varying levels of specialists providing primary care services, having four years of experience in the Medicare Shared Savings Program was consistently associated with lower spending when compared to having one to three years of experience.

Conclusions and Relevance:

The optimal portion of specialists providing primary care services - to reduce spending - was found to be 35% to 40%. These findings suggest that integrating specialists in to the activities and objectives of MSSP ACOs could lead to lower spending and better performance.


First Advisor

David L. Chin

Second Advisor

Michael E. Begay