The impact of patient-centered medical home certification on quality of care for patients with diabetes.

Our results suggest that the initial cohort of certified practices was already performing at a high level before certification, perhaps requiring little change in their operations to achieve PCMH certification. The second cohort, on the other hand, made meaningful, quality-improving changes in the years surrounding certification. Differences by cohort may partially explain the inconsistent PCMH impacts found in the literature.