Despite projections of an oversupply of residency-trained emergency medicine physicians by 2030 and amidst intensifying national debate over Nurse Practitioner (NP) qualifications to practice independently and unsupervised, NPs are increasingly staffing Emergency Departments (EDs) as hospitals seek to contain costs while simultaneously expanding services. We sought to characterize NP practice in the ED by examining NP independent billing by level of severity of illness, and relationship to practice authority, State Medicaid expansion status, and rurality.

Medicare provider utilization and payment data between 2015–2018 was used to explore NP billing as compared to five other clinician provider types for common emergency services acuity codes (CPT codes 99281–99285) to determine services billed for levels of severity of illness and trends over time. Number of services billed by clinician provider type related to state policies on NP practice authority, location, and population characteristics was explored.

NPs who independently billed for ED CPT codes (99282–99285), increased during this time and decreased for acuity code 99281 (minor and self-limiting). Overall, NPs saw a greater increase than all other providers in both the highest severity CPT codes of 99284 and 99285.

The analysis revealed that type of clinician, state practice authority policy, number of NPs, and percent of population 65 years and older (by zipcode) and population size are positive predictors for services billed. The negative predictors were rurality, states which accepted the Medicaid expansion, having a higher number of non-English speaking residents, and non-emergency medicine clinicians.

As a proportion of the providers independently billing in the ED, NPs are increasingly managing higher acuity patients as evidenced by billing percentage of the highest acuity CPT codes (99284 and 99285). During the same time period, ED MDs decreased their billing in the same categories. Current employment of NPs in the ED may not be fulfilling its original vision to care for the lower acuity patients in order to allow MDs to care for the more acutely and critically ill patients, and to increase the services for underserved populations in rural areas, those over age 65, and those with limited English language proficiency. Future research should investigate ED policies resulting in NPs as opposed to MDs seeing patients with greater severity codes.