QuestionÌý Was implementation of primary care–focused Medicaid accountable care organizations (ACOs) in Massachusetts followed by improved care for Medicaid-insured vs privately insured children with asthma?

FindingsÌý This difference-in-differences cross-sectional study among 376 509 child-year observations found no change in routine asthma visits, an increase in appropriate asthma medication ratios, and an increase in emergency department or hospital use for Medicaid-insured vs privately insured child-years following Medicaid ACO implementation.

MeaningÌý During the first 3 years of Massachusetts’ Medicaid ACO program, there was no clear evidence of success at reducing disparities in asthma care and outcomes for children insured by Medicaid compared to children with private insurance.

ImportanceÌý Nearly 6 million children in the US have asthma, and over one-third of US children are insured by Medicaid. Although 23 state Medicaid programs have experimented with accountable care organizations (ACOs), little is known about ACOs’ effects on longstanding insurance-based disparities in pediatric asthma care and outcomes.

ObjectiveÌý To determine associations between Massachusetts Medicaid ACO implementation in March 2018 and changes in care quality and use for children with asthma.

Design, Setting, and ParticipantsÌý Using data from the Massachusetts All Payer Claims Database from January 1, 2014, to December 31, 2020, we determined child-years with asthma and used difference-in-differences (DiD) estimates to compare asthma quality of care and emergency department (ED) or hospital use for child-years with Medicaid vs private insurance for 3 year periods before and after ACO implementation for children aged 2 to 17 years. Regression models accounted for demographic and community characteristics and health status. Data analysis was conducted between January 2022 and June 2024.

ExposureÌý Massachusetts Medicaid ACO implementation.

Main Outcomes and MeasuresÌý Primary outcomes were binary measures in a calendar year of (1) any routine outpatient asthma visit, (2) asthma medication ratio (AMR) greater than 0.5, and (3) any ED or hospital use with asthma. To determine the statistical significance of differences in descriptive statistics between groups, χ² and t tests were used.

ResultsÌý Among 376 509 child-year observations, 268 338 (71.27%) were insured by Medicaid and 73 633 (19.56%) had persistent asthma. There was no significant change in rates of routine asthma visits for Medicaid-insured child-years vs privately insured child-years post-ACO implementation (DiD, −0.4 percentage points [pp]; 95% CI, −1.4 to 0.6 pp). There was an increase in the proportion with AMR greater than 0.5 for Medicaid-insured child-years vs privately insured in the postimplementation period (DiD, 3.7 pp; 95% CI, 2.0-5.4 pp), with absolute declines in both groups postimplementation. There was an increase in any ED or hospital use for Medicaid-insured child-years vs privately insured postimplementation (DiD, 2.1 pp; 95% CI, 1.2-3.0 pp), an 8% increase from the preperiod Medicaid use rate.

Conclusions and RelevanceÌý Introduction of Massachusetts Medicaid ACOs was associated with persistent insurance-based disparities in routine asthma visit rates; a narrowing in disparities in appropriate AMR rates due to reductions in appropriate rates among those with private insurance; and worsening disparities in any ED or hospital use for Medicaid-insured children with asthma compared to children with private insurance. Continued study of changes in pediatric asthma care delivery is warranted in relation to major Medicaid financing and delivery system reforms.