Determinants of primary care physicians' referral pattern: a structural equation model approach.

This study examines patient referrals by primary care physicians (PCP) with nurse practitioners and physician assistants (NP-PA) in their medical practices as compared to practices without them. The study uses data from the Robert Wood Johnson Foundation community tracking study (CTS) Physician Survey, Round I (1996-97) and II (1998-99). Structural equations with binary dependent variables were used to examine the links among managed care, the use of NP-PA, the complexity of patient's conditions, and the number of referrals. PCP's with NP-PA were found to have a greater likelihood of treating patients with complex conditions instead of referring them to specialists. Managed care related variables (i.e., large group practice/HMO, the percentage of patients for whom PCPs acted as gatekeepers, and the percentage of managed care revenue from capitated/prepaid contracts) affected PCP' patient referrals, but only through the increased use of NP-PA. PCP's with NP-PA were also found to provide appropriate care to the complex patients. These findings indicate that NP-PA enable PCP to concentrate on patients with more complex conditions thus reducing the number of referrals. In addition, NP-PA is found to affect the gatekeeper role of PCPs.