The Role of Organizational Affiliations in Physician Patient-Sharing Relationships.

Provider consolidation may enable improved care coordination, but raises concerns about lack of competition. Physician patient-sharing relationships play a key role in constructing patient care teams, but it is unknown how organization affiliations affect these. We use the Massachusetts All Payer Claims Database to examine whether patient-sharing relationships are associated with sharing a practice site, medical group, and/or physician contracting network. Physicians were 17 percentage points more likely to have a patient-sharing relationship if they shared a practice site and 4 percentage points more likely if they shared a medical group, as compared with sharing no affiliation. However, there was no detectable increased probability of a patient-sharing relationship within the same physician contracting network. Our finding that physician patient-sharing relationships are concentrated within organizational boundaries at practice site and medical group levels helps illuminate referral incentives and provide insight into the role of organizational affiliations in patient care team construction.