Meyers DJ, et al. - Researchers investigated the association of a team-based primary care transformative collaborative initiative with patient healthcare use and costs. Using difference-in-differences, they compared pre-utilization and post-utilization rates between intervention and comparison practices with inverse probability weighting to balance observable differences. They included 83,953 patients accounting for 138,113 patient-years across 18 intervention practices, and 238,455 patients accounting for 401,573 patient-years across 76 comparison practices. Practices partook in a 4-year learning collaborative that developed and supported team-based primary care. Although team-based care was not associated with differences in the full patient sample, there was a subset of chronically ill patients that displayed substantial reductions in utilization. Hence, team-based care practice transformation in primary care settings may have utility for improving the care of patients of greater illness severity, thereby decreasing avoidable use. However, among healthier patients, it may lead to greater use.