Nurse practitioners (NPs) and PAs working independently in emergency departments used fewer resources and less low-value care than physicians, and NPs/PAs working in collaboration with physicians used more resources and low-value care than physicians working alone, according to an analysis of nationally representative data on practice patterns published in BMJ Open.

“Our findings suggest that NPs/PAs seeing patients alone may be more efficient than physicians alone, whereas NPs/PAs seeing patients in collaboration with a physician are less efficient than physicians alone,” said lead author John N. Mafi, MD, MPH, associate professor of medicine in the Division of General Internal Medicine and Health Services Research at the David Geffen School of Medicine at UCLA.

“These findings have important implications for policymakers and health system leaders interested in improving access to emergency care, while also not worsening the efficiency and appropriate use of care delivery,” Dr Mafi said. “For example, our findings suggest that NPs/PAs seeing more complex patients used more services than physicians alone, but the converse might be true for more straightforward patients. Of course, it is important to note that we only evaluated one narrow aspect of quality of care such as efficiency and appropriateness of care, and that health system leaders must consider many other factors when determining how best to integrate NPs and PAs into ED settings.” 

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Researchers Analyzed NHAMCS Data to Compare Practice Patterns

The study is based on an analysis of nationally representative data from the National Hospital Ambulatory Medical Care Survey (NHAMCS) on ED visits to compare practice patterns among NPs/PAs and physicians. The analysis was based on data from 177,657 ED visits among adults aged 18 years and older who presented with any complaint between January 1, 2009, and December 31, 2017.

The researchers compared outcomes among ED visits conducted by NPs/PAs alone, NPs/PAs in collaboration with a physician, and physicians alone. The primary outcome measure was overall use of services such as diagnostic tests, procedures (eg, suturing), medications prescribed during the visit or at discharge, length of time per visit (from time of ED arrival to discharge), and likelihood of hospitalization. Secondary outcomes were use of the following services considered to be of low value, based on clinical practice guidelines such as Choosing Wisely:

  1. Antibiotics for upper respiratory infections without alarm features (eg, chronic obstructive pulmonary disease [COPD]) or skin abscesses without alarm features (eg, cellulitis or signs of sepsis)
  2. Plain radiography for back pain without alarm features (eg, cancer, trauma, or neurologic deficit)
  3. Diagnostic imaging with magnetic resonance imaging (MRI) and computed tomography (CT) for back pain or headache without alarm features (eg, trauma, cancer, and neurologic deficit)
  4. Opioids for back pain or headache without alarm features (eg, cancer and trauma)
  5. Inappropriate prescribing of medications among older adults

The researchers took several steps to control for potential selection bias of NPs/PAs seeing patients with lower complexity conditions such as using propensity score matching and performing sensitivity restricted to EDs in which more than 95% of visits included NP/PA-physician collaboration.

NP/PAs Collaborating With Physicians Used More Resources

“When NPs/PAs practiced alone they tended to use less care, whereas when NPs/PAs practiced in collaboration with a physician they utilized more care,” than did physicians practicing alone, Dr Mafi said (Tables 1 and 2). The latter finding was confirmed with extensive sensitivity analyses; the authors were unable to independently verify the former finding, he said.

The findings on NPs/PAs practice patterns are limited by the inability to randomly assign patients to providers to eliminate selection bias, the study authors noted. While they were not able to independently verify the finding that NPs/PAs alone deliver less care than physicians, “our findings are consistent with NPs/PAs-alone delivering fewer services than physicians for simpler and more algorithmic cases. Our sensitivity analyses of low triage acuity visits, where fewer resulted in visits including the NP/PA–physician combination, is consistent with this hypothesis. Such findings are also consistent with the broader primary care literature (including our own work), where primary care NPs/PAs appear to practice at similar or better efficiency of care than physicians for less emergent/complex conditions.”

Table 1. Overall Resource Utilization During Emergency Department Visits

OutcomePhysician (reference)NP/PA AloneNP/PA-Physician
Time per visit (min)267.6245.9 (P =.02)289.8 (P <.001)
Number of medications  2.802.62 (P =.002)3.08 (P <.001)
Number of diagnostic tests4.663.77 (P <.001)5.07 (P <.001)
Number of procedures0.770.67 (P <.001)0.86 (P <.001)
OR of visits resulting in hospitalizationReference (n=143687)0.35 (P <.001)1.33 (P <.001)
OR, odds ratio
Adapted from Mafi et al.

Table 2. Practice Patterns on Low-Value Health Services Used in Emergency Departments

ServicePhysician sample size (reference)NP/PA Alone (aOR)NP/PA-Physician (aOR)
CT/MRI for uncomplicated back pain or headache17,7240.651.23
Antibiotics for uncomplicated URI54551.21.05
Inappropriate medications for older adults30,4610.930.98
Opioid medications for uncomplicated back pain or headache15,5250.811.11
Inappropriate antibiotics for simple UTIs45360.890.92
Plain radiography for uncomplicated back pain10,0490.91.11
CT, computed tomography; MRI, magnetic resonance imaging; URI, upper respiratory infection
Adapted from Mafi et al.

Should NP and PA Practice Patterns be Studied Separately?

Lamont Hunter, MPH, PA-C

The findings “should support increased utilization of PAs and NPs working at the top of their license in emergency departments,” commented Lamont Hunter, MPH, PA-C, who is immediate past president of the Society of Emergency Medicine Physician Assistants (SEMPA) and was not affiliated with the study. 

Mr Hunter said that while there is utility in comparing practice patterns between professions, “the conclusion of the study would be much more credible and impactful if it had separated the PA and NP professions in its methods.”

“The PA and NP professions are different and each have unique characteristics that should be highlighted separately. For example, PAs are trained in a medical model with rigorous and standardized education and accreditation. Nurse practitioners are trained in a nursing model, often relying on previous nursing experience to supplement and complement their graduate training. By studying PA and NP clinical outcomes separately, the conclusions may be more impactful and may be able to help identify areas where each profession needs to improve. Although PAs and NPs are often combined under an umbrella of advanced practice providers [APPs], it is important to study each profession individually.”

“While we acknowledge that NPs and PAs undergo different training, NP and PA practice patterns were largely indistinguishable in terms of study outcomes in our paper,” as shown in the online supplemental appendix, Dr Mafi said. “In other words, NPs and PAs looked very similar in terms of utilization of care, so it was reasonable to combine them into a single variable,” Dr Mafi noted. Separating the 2 fields also increases the amount of statistical testing required in the study, increasing the chance for false positive findings from multiple testing, he said.

Commenting on the finding that PA-NP/physician combinations used more resources compared with PAs/NPs alone and physicians alone, Mr Hunter said that while “team-based, collaborative practice is a hallmark of emergency medical care and should not be abandoned, whenever more clinicians are involved, inefficiencies can arise.”

“I think you can balance these potential inefficiencies by empowering PAs and NPs with expanded scope of practice and additional training to care for patients as well as we can,” Mr Hunter concluded.


Mafi JN, Chen A, Guo R, Choi K, Smulowitz P, Tseng CH, Ladapo JA, Landon BE. US emergency care patterns among nurse practitioners and physician assistants compared with physicians: a cross-sectional analysis. BMJ Open. 2022;12(4):e055138. doi:10.1136/bmjopen-2021-055138