The physician assistant (PA) and NP professions both developed in the United States in the 1960s.1 After half a century, it seems timely to examine how they compare and consider potential interchangeability more closely. Reasons for this analysis include providing labor economists with information on the margin of substitutability for productivity purposes and providing human resource managers with data on alternatives for filling professional shortages.
Historically, the debate about PAs and NPs has centered on differences in education, background, and training, and strong opinions can be found on both sides.2,3 We offer a novel point of view in this commentary, focusing on the legal development of the two professions and taking a functional approach in examining their interchangeability. Though the legal development of the two occurred along parallel tracks, we argue that PAs and NPs in the United States are functionally substitutable in many practice settings.
Both PAs and NPs provide healthcare and generate patient outcomes that are mainly the same (to one another and physicians).4,5 Moreover, patients see the two professions as largely indistinguishable.6-8 That NPs deliver extended care under the nursing model and PAs deliver medical care under the medical model may be better understood as a legal idiosyncrasy than as an indicator that the two professions supply meaningfully different healthcare services. State medical practice acts initially would have prevented both PAs and NPs from diagnosing patients, ordering tests, performing procedures, and prescribing medication. Although PAs and NPs do all of these things today, the legal pathways to this practice were different for the two professions. Legislatures often folded PAs and their ability to deliver care into existing medical practice acts. These same legislatures, perhaps seeing NPs as more highly trained nurses, often extended state nursing practice acts (coupled with changes to the state medical practice act) to grant NPs authority historically reserved to physicians.
Though the legislative path to practice differed for the two professions—indeed, legislatures rarely extend the scopes of practice of PAs and NPs simultaneously—the services provided by PAs and NPs are substitutable to a far greater extent than those of most overlapping professions, such as radiological technology or orthopedics.9 Although no empirical evidence on whether PAs and NPs are economic substitutes has been produced, other surrogate markers for interchangeability exist. For example, the wages of PAs are sensitive to the laws governing NPs (and vice versa), suggesting some degree of interdependence.10,11 From the patient's perspective, there may be little difference. Even when PAs and NPs are not competing for the same technical domain, the demand for services seems to be greater than their supply.12,13 If a patient's needs are met, few patients generally care who treats them.14,15
Different social theories may explain why PAs and NPs are on parallel legal tracks but are seemingly indistinguishable to observers of healthcare labor. Under one theory, the pressures from the demand for services, contemporary management philosophies, and a greater emphasis on consumer preferences can result in a somewhat haphazard allocation of legal authority across multiple actors.16 The other theory is that incumbent professionals initially resist the adoption of policy innovations through the construction of market entry barriers by using state regulatory power or by withholding critical resources.17 This control results in professional groups claiming authority over bodies of knowledge and specific tasks. But with increasing demand for healthcare services, the need to augment care can overcome this resistance.
From our economic perspective, PAs and NPs in family or general medicine are virtually indistinguishable in their roles and are interchangeable in a variety of settings.4,18-21 Where they might differ, such as specific specialty settings (for example, in the military, a PA can be a combat medical officer or independent on a polar-bound ice breaker), the difference is at the margin. Moreover, though PAs may find it easier to switch roles than NPs, who are educated and certified in a particular specialty, the professions overall supply many of the same healthcare services producing the same outcome at the same cost of care for complex patients.22 Although some outcome studies may illustrate minor differences and some efficiency studies may reveal different productivities, these two types of clinicians look and act far more similarly than differently.
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