The Impact of Using Mid-level Providers in Face-to-Face Primary Care on Health Care Utilization.

Background: There has been concern that greater use of nurse practitioners (NP) and physician assistants (PA) in face-to-face primary care may increase utilization and spending.

Objective: To evaluate a natural experiment within Kaiser Permanente in Georgia in the use of NP/PA in primary care.

Study Design: From 2006 through early 2008 (the preperiod), each NP or PA was paired with a physician to manage a patient panel. In early 2008, NPs and PAs were removed from all face-to-face primary care. Using the 2006-2010 data, we applied a difference-in-differences analytic approach at the clinic level due to patient triage between a NP/PA and a physician. Clinics were classified into 3 different groups based on the percentage of visits by NP/PA during the preperiod: high (over 20% in-person primary care visits attended by NP/PAs), medium (5%-20%), and low (<5%) NP/PA model clinics.

Measures: Referrals to specialist physicians; emergency department visits and inpatient admissions; and advanced diagnostic imaging services.

Results: Compared with the low NP/PA model, the high NP/PA model and the medium NP/PA model were associated with 4.9% and 5.1% fewer specialist referrals, respectively (P<0.05 for both estimates); the high NP/PA model and the medium NP/PA model also showed fewer hospitalizations and emergency department visits and fewer advanced diagnostic imaging services, but none of these was statistically significant.

Conclusions: We find no evidence to support concerns that under a physician's supervision, NPs and PAs increase utilization and spending.