US emergency care patterns among nurse practitioners and physician assistants compared with physicians: a cross-sectional analysis

Objectives: Nurse practitioners and physician assistants (NPs/PAs) increasingly practice in emergency departments (EDs), yet limited research has compared their practice patterns with those of physicians.

Design, setting and participants: Using nationally representative data from the National Hospital Ambulatory Medical Care Survey (NHAMCS), we analysed ED visits among NPs/PAs and physicians between 1 January 2009 and 31 December 2017. To compare NP/PA and physician utilisation, we estimated propensity score-weighted multivariable regressions adjusted for clinical/sociodemographic variables, including triage acuity score (1=sickest/5=healthiest). Because NPs/PAs may preferentially consult physicians for more complex patients, we performed sensitivity analyses restricting to EDs with >95% of visits including the NP/PA-physician combination.

Exposures: NPs/PAs.

Main outcome measures: Use of hospitalisations, diagnostic tests, medications, procedures and six low-value services, for example, CT/MRI for uncomplicated headache, based on Choosing Wisely and other practice guidelines.

Results: Before propensity weighting, we studied visits to 12 410 NPs/PAs-alone, 21 560 to the NP/PA-physician combination and 143 687 to physicians-alone who saw patients with increasing age (41, 45 and 47 years, p<0.001) and worsening triage acuity scores (3.03, 2.85 and 2.67, p<0.001), respectively. After weighting, NPs/PAs-alone used fewer medications (2.62 vs 2.80, p=0.002), diagnostic tests (3.77 vs 4.66, p<0.001), procedures (0.67 vs 0.77, p<0.001), hospitalisations (OR 0.35 (95% CI 0.26 to 0.46)) and low-value CT/MRI studies (OR 0.65 (95% CI 0.53 to 0.80)) than physicians. Contrastingly, the NP/PA-physician combination used more medications (3.08 vs 2.80, p<0.001), diagnostic tests (5.07 vs 4.66, p<0.001), procedures (0.86 vs 0.77, p<0.001), hospitalisations OR 1.33 (95% CI 1.17 to 1.51) and low-value CT/MRI studies (OR 1.23 (95% CI 1.07 to 1.43)) than physicians-results were similar among EDs with >95% of NP/PA visits including the NP/PA-physician combination.

Conclusions and relevance: While U.S. NPs/PAs-alone used less care and low-value advanced diagnostic imaging, the NP/PA-physician combination used more care and low-value advanced diagnostic imaging than physicians alone. Findings were reproduced among EDs where nearly all NP/PA visits were collaborative with physicians, suggesting that NPs/PAs seeing more complex patients used more services than physicians alone, but the converse might be true for more straightforward patients.