Limitations
This study had several limitations. First, it was not randomized. It is possible that there were unmeasured differences in the 2 study groups that we did not control for in our analysis. Considering that only 17.4% of eligible ACO patients participated in the trial, our findings might not be generalizable to all patients with high utilization and high cost from ACOs in safety-net institutions. Our sensitivity analyses and post hoc subgroup analyses did not have enough sample size to achieve statistical power. Data on patient race and ethnicity were collected in the routine course of clinical care via a combination of self-report and determination by hospital staff and therefore may be inaccurate. Finally, usual care in our study included a pharmacy liaison and a clinic-based navigator. Such staff may not be available in most primary care settings, thereby limiting generalizability of our findings. However, our intervention may be effective when implemented in clinics with fewer ancillary staff.