On April 1, 2016, two counties in Southwest Washington (Clark and Skamania) became the first region in Washington to adopt an integrated managed care (IMC) model. This evaluation examines the impact of the transition to IMC on the health and social outcomes of Medicaid beneficiaries in the IMC region. Difference-in-difference approaches were used to examine changes in a broad set of health care performance metrics in the first year after implementation of the IMC model (April 1, 2016 to March 31, 2017), relative to beneficiary experience in the prior year. We report findings derived from both simple t-tests and generalized estimating equation (GEE) models that control for the potential confounding effect of regional differences in beneficiary characteristics. Of the health and social outcome metrics examined, two-thirds showed no significant relative change in Southwest Washington, compared to the balance of state. The outcome measures that had significant differences were mostly positive for the Southwest region, with few statistically significant negative results.
