The Effect of Nurse Practitioner Scope of Practice Legislation on Primary Care Delivery

Demand for primary care services is projected to grow considerably in the next decade. Advanced practice clinicians such as nurse practitioners (NPs) may be able to help meet this growing demand. NPs are registered nurses with advanced education and training, and in 23 states they are legally authorized to practice and prescribe independently. In all other states, scope of practice (SOP) laws require NPs to practice with some degree of physician oversight.

NP SOP is a topic of considerable debate. Proponents of full NP SOP (i.e. no requirements for physician oversight) argue it allows NPs to practice at the top of their license and increases access to care for patients. Opponents believe NPs are not adequately trained to treat complex patients. Research has found full NP SOP may improve population health and access outcomes, with minimal effects on expenditures. However, data availability has limited researchers’ ability to examine empirically the relationship between SOP and the actual delivery of primary care by NPs, including whether and how practices reorganize when SOP laws expand.

In this study, I examine time-series variation in NP SOP laws to estimate the effects of expanded NP SOP on the number of NPs employed, the division of patient visits between NPs and physicians, and the frequency of NP-provided services billed incident to physicians at primary care practices. I use a large national dataset of all-payer claims linked to electronic health records from athenahealth, Inc. I estimate two-way fixed effects models and use an event study framework to compare trends in eight states that granted full NP SOP between 2011 and 2017 to those that had restricted SOP in 2011 and did not expand it between 2011-2017.

The analytic sample includes 17,356 office-based primary care practices, including 461 practices located in states that expanded NP SOP between 2011 and 2017. In cross-sectional analyses, I find full SOP is associated with increased use of NPs. In states with full SOP, more practices have at least one NP (42% vs. 38% of practices); NPs initiate a greater share of patient appointments at their practices (22% vs. 19%); and NPs bill incident to physicians less often (25% vs. 36%), relative to states with restricted SOP. However, the regression and event study results suggest there is substantial heterogeneity in practices’ responses to SOP expansions. The estimated effects of full SOP are not statistically significant when pooled across all practices and time periods.

This study’s preliminary findings suggest that expanding NP SOP has the potential to facilitate multidisciplinary primary care delivery and may affect the way NPs bill for their services. Further research is needed to understand the heterogeneity in practices’ responses to SOP and the relationship between SOP and the nature of care provided by NPs and physicians. This line of research will inform policymakers as they respond to ongoing primary care workforce and delivery system challenges.