Secondary Logo

Journal Logo

AAPA Members can view Full text articles for FREE. Not a Member? Join today!
Original Research

Research on the PA profession

The medical model shifts

Dehn, Richard W. MPA, PA-C, DFAAPA; Everett, Christine M. PhD, MPH, PA-C; Hooker, Roderick S. PhD, MBA, PA

Author Information
Journal of the American Academy of Physician Assistants: May 2017 - Volume 30 - Issue 5 - p 33-42
doi: 10.1097/01.JAA.0000515548.76484.39
  • Free



Research on the physician assistant (PA) profession is at a crossroads of development—successful as an innovation but unsure of new directions. The PA arose out of ideas that another set of skilled hands could improve the delivery of physician services. The evidence is that PAs may be functioning beyond expectations. Questions of how PAs function is observed through multiple approaches of research: sociological, economic, historical, educational, anthropological, organizational, and health services research. On the occasion of the PA profession's 50th anniversary, the question arises as to what PA research has shown the world, and where it might be heading.

When the PA profession first developed, little was known about this vocation. After PAs gained initial credibility, historical documents emerged suggesting that prototype PAs were abundant in the world with different names, origins, and functions. As of 2017, PAs are found in a number of countries and their documentation is slowly accumulating.1

This study is an attempt to offer some context of PA-focused research spanning the first half-century of the profession and how various investigations may have contributed to the understanding of what PAs are and what they do. A bibliographical search on the literature found more than 6,000 titles specific to PAs or health professionals comparable to PAs. This field was narrowed to about 700 studies that contributed to advancing the benefits of PAs to the societies they occupy. Three eras emerged naturally that tend to illustrate the marked evolution of research (Table 1).

Historical research eras in the PA profession


The early years of PA research are characterized by defining a construct (that is, PAs) more than providing evidence. Early writers theorized whether there should be PAs, identifying that such an assistant was needed, and suggesting various names, even before there were US PAs.2 The notion of using health practitioners who were not physicians to provide medical services was not new. Amos Johnson, MD, a solo practitioner in Garland, N.C., had an assistant, Henry Lee “Buddy” Treadwell, whom he trained and occasionally left alone to manage his medical practice.3 (See PA prototype—the legacy of Buddy Treadwell in the March issue of JAAPA.) Other PA prototypes included the assistant medical officer in Micronesia, Fiji, and Papua, New Guinea; the apothecary in Ceylon; the public health worker in Ethiopia; the clinical assistant in Kenya; the barefoot doctor in China; the practicante in Puerto Rico; the rural nurse in Cuba; the officier de santé in France; and the feldsher in Eastern Europe. All had been clinicians in use before the contemporary PA emerged (Table 2). In the United States, one proposal was the term assistant medical officer to describe a type of healthcare worker almost identical to today's PA.4,5

Types of health professionals in various countries

PAs were introduced in the United States in the mid-1960s.6 That three prominent academic physicians introduced the US PA almost simultaneously and equidistant across the continent in three highly respected academic medical centers is curious, yet there is no evidence they knew each other.7 This historical event occurred initially at Duke University in Durham, N.C. From the onset, interest in PA activity was almost immediate, both to satisfy that PAs could be what the early creators envisioned, and to capture what many thought was a historical achievement.8-17 In the same decade, Henry Silver, MD, and Loretta Ford, RN, introduced the child health associate in Colorado and Richard A. Smith, MD, MPH, the MEDEX health professional in Washington State.18,19 A handful of colleges and universities soon followed with their own PA programs. Interestingly, these programs never aligned with each other.20,21 But, as each program developed, they produced research documents that serve to anchor the history.22-29

A great deal of health services research was performed during the 1970s and 1980s examining the effect of introducing PAs into medical practices. Sometimes these were case control studies and sometimes the investigators compared the productivity of small practices before and after introducing a PA.30 The Bureau of Health Professions in the Department of Health, Education, and Welfare (now the Department of Health and Human Services) underwrote much of this research. After a decade, more than 60 research publications revealed that PAs were well accepted, safe, and effective practitioners in medical care delivery. Studies also showed that patient acceptance of the PA role was high and that most PAs worked in general medical care practices in medically needy areas.31-36

Many of the seminal evaluations of PA use were performed in ambulatory care practices and in health maintenance organizations (HMOs). In such settings, PA clinical performance was impressive. Their productivity (number of patient visits) approached and sometimes exceeded that of family medicine physicians. PA productivity rates in a large group model HMO showed that the physician/PA substitutability ratio, a measure of overall clinical efficiency, was 76%.31,37,38 A review of the literature examining the issue of delegation in the 1970s identified 10 studies that used office visits as an output measure (Table 3). In the aggregate, the range of delegation (also known as task transfer) was broad, 6% to 99%, with considerable overlap even within a single setting or time of observation.31-36,38,39

Delegation of office visits to PAs: Summary of observations from 1971 to 1978

By the end of the first decade of PA implementation, experience and empirical research indicated that US medicine's adoption of PAs had been generally positive. PAs were responsive to the public and the medical mandate to work in generalist and specialist care roles in medically underserved areas. They were gaining recognition as being competent, effective, and clinically versatile healthcare providers after major health research studies revealed their clinical effectiveness.40 Research began to appear on PAs, their behaviors, and their comparisons to physicians. Experiments involving hypotheses and manipulation of variables began to drive the research. The critics became fewer in number.

Questions of economy and value have been paramount to the profession: Are PAs cost-effective? Do they provide high-quality care? Many of the findings undertaken in the early days of the PA profession were intended to answer those questions.40 Out of this and other work came reports that PAs are competent, provide physician-comparable healthcare services at lower cost, and in some instances are superior to physicians in some areas of quality.41 Although PA cost-effectiveness in this early period was never considered conclusive in all clinical practice settings, substantial empirical research confirmed that PAs are cost-effective in most settings.42-44 The most significant statement about this era is that it is highly unlikely PAs would have been employed if they were not cost-effective.

Evidence indicates that the organizational setting is closely related to the productivity and possible cost benefits of PA use. Scheffler documented that PAs employed in institutional settings were more productive than those in private practice and saw more patients in the same period of time.45 Record's seminal work noted correlations among productivity, delegation of tasks, and organizational size; she and her collaborators proposed that personnel economies of scale and cost savings incentives were the likely explanations for their observations in HMOs.37 By 1980, Record had predicted that PAs could skillfully assume at least 84% of all ambulatory medical care services in the United States; her findings were published in the book Staffing Primary Care in the 1990s.37


By the late 1970s, the profession was reaching a point of stabilization around the advocated concept of a primary care model and a minimum of training defined by accreditation standards that were sponsored by the American Medical Association.46 Just when PA development was underway, an influential event occurred—the 1980 release of the Graduate Medical Education National Advisory Committee (GMENAC) report predicted physician surpluses, which resulted in a substantial retrenchment in the training of all health professionals.47,48 The healthcare workforce cutback was so extreme that it was not unusual to hear discussions as to whether PAs would be necessary. Following the release of the GMENAC report and until the early 1990s, PA program enrollment was flat, graduating about 1,200 PAs annually, and only a few new PA programs were established.49,50

This phase of PA research concentrated on describing the spread of the profession into other specialties, its activity throughout the healthcare workforce, its educational processes, and its use. As an extension of the early research that documented the role, value, and acceptance of PAs in a variety of clinical settings, PA educators, researchers, and supporting organizations turned to the task of describing the profession and its educational system. During this period, many of the early studies on PA acceptance were small-scale local projects. The defining characteristic of this phase was the success in establishing generalizable large-scale surveys of a national scope that were performed regularly, thus documenting the profession and its changes over time.

When the First Annual Report on Physician Assistant Educational Programs in the United States, 1984-85, was published by the Association of Physician Assistant Programs (APAP), it was the initial detailed description of the education landscape.50 Later, a summary of the report was published in the Journal of Medical Education.51 With minor revisions, a Report on Physician Assistant Educational Programs in the United States has been undertaken annually, creating a rich trove of trend data for scholars and educators.51,52

Although the annual census of PAs could be estimated from those who passed the Physician Assistant National Certifying Exam (PANCE), researchers had no way to determine how many of those PAs were in clinical practice or what they did. The first effort to collect data on this population was the 1981 publication of the 1978 APAP national survey of PAs undertaken by Henry Perry.53 In 1990, the American Academy of PAs (AAPA) piloted its first national survey of all PAs, administered to AAPA members from 1991 through 1994. Beginning in 1995, the AAPA Census was mailed to all individuals eligible to practice as PAs, and summary results of these data from 1996 onward are publically available.54

In this post-GMENAC retrenchment phase, a 1986 publication from Congress' Office of Technology Assessment (OTA) concluded that the contributions of PAs, NPs, and certified nurse-midwives (CNMs) were competent and substantial, and recommended that the professions be expanded by providing funding for their services.41 Although perhaps overly optimistic in its conclusions, the OTA report was welcome news to a profession that had been experiencing relatively stagnant growth and worrying if it was irrelevant.55 Additionally, data published from a large HMO in 1986 again validated positive physician attitudes about PAs (Figure 1).56

Comparison of physician attitudes toward use of NPs and PAs56

PA educators performed studies to address specific questions important to the profession's viability. Denis Oliver and Reginald Carter analyzed the 1981 APAP national survey of PAs, and published articles describing PA salaries and documenting discrepancies in PA salaries by sex.57-59 At the time, PA educators were collecting students' experiences following graduation, which anecdotally described the contribution of PAs to the healthcare delivery system.53 This was self-serving evidence that the educational processes were appropriate.19,60 Some research was published addressing specific questions of educational effectiveness, but typically these efforts were one-program studies with limited generalizability. One survey studied the attitudes of supervising physicians, physicians in family practice residency training, and sophomore medical students about the need for PAs, the quality of PA training, and the specific services each of these groups felt could be best provided by a PA; another compared the performance of medical students and PA students in interdisciplinary courses.61

Starting in the mid-1990s, the number of PA programs and the number of students enrolled and graduated increased dramatically. This was at first in response to increasing demand for PAs due to early healthcare reforms and the emergence of the managed care funding model that readily employed PAs. Later the demand was in response to restrictions on medical resident work hours and the need to back fill house officer (resident) shortages with PAs.62 PA educational programs also began a rapid transformation from conferring a certificate or undergraduate degree to the graduate level award of a master's degree. The resulting large influx of graduating cohorts possessing an entry-level master's degree changed the size and demographics of the profession in a relatively short time. However, despite this transformation and a substantial increase in the number of PAs and PA faculty with graduate degrees, the proportion of PA faculty who have performed any scholarly activity has remained constant at about one-third.63,64 PANCE scores, the only easily obtainable outcome measurement all US PA graduates have in common, have been studied by many to determine whether program characteristics or student characteristics affect scores or pass rates. McDowell and colleagues studied the correlation between PANCE scores and program variables.65 Hooker and colleagues investigated a 5-year aggregate of PANCE scores for correlation of performance to individual or program characteristics, and Asprey and colleagues looked at three PANCE cohorts 5 years apart to see whether changes in program characteristics, individual characteristics, or the granting of a master's degree were correlated with PANCE scores or pass rates.66-68

Until 2000, most PAs had practiced in outpatient settings, as PAs were not commonly used in hospitals. This was due to a general lack of reimbursement for inpatient PA services. The exception was in postgraduate education programs where PAs were often used as house officers.69 The passage of HR 2015, the Balanced Budget Act of 1997, provided payment for PA (as well as NP and CNM) services at 85% of the physician rate in all settings.70 This created a funding stream for inpatient PA practice, resulting in increasing opportunities in medical specialties. New PA graduates choosing primary care jobs fell from 62% in 1996 to 34% in 2003, perhaps due in part to this new revenue stream for specialty practices.70 The increased number of new PA graduates expanding throughout the healthcare delivery system, estimated to total 4,475 in 2004, also raised concern about the effect of PAs on medical liability and malpractice litigation.71,72 Several studies were published that documented that the legal risk of using PAs was relatively low.73,74 However, as PAs increased in number and populated a greater proportion of healthcare delivery clinicians, the remaining unanswered question at the start of the new millennium was an old familiar one: What financial value do PAs contribute to the healthcare team?


For many, the work to date had provided convincing evidence that the PA model was changing the environment of medicine. PAs were seen as an innovation in medical care delivery where shortages in underserved populations could be readily addressed.75 Perhaps there were simply enough PAs in the workforce to expose sufficient numbers of patients to a positive experience. With time, perhaps a critical mass effect was reached, making it clear that the profession was a permanent part of the healthcare landscape. Or perhaps PAs had entered a new era in healthcare delivery that medicine was a shared occupation. At the same time, the cost of healthcare was rising at an unsustainable rate in the United States and something was needed to address this problem.76 Despite outspending all other countries, the United States had care that was not as good as that in comparable nations.77 With the aging US population and increases in the prevalence of chronic illnesses, policy makers had serious concerns about the health of the healthcare system.78 Managed care had ended, and policy makers were debating how to redesign a system to address these trends. More people needed access to care, quality needed to improve, and costs needed to go down—thus the Triple Aim was born.76 With these goals in mind, health delivery being restructured, and projected physician shortages, team-based care was the phrase on everyone's lips. Likely it was a combination of those influences, but many sounded the call for greater reliance on PAs.79-82

This call for greater reliance of PAs in team-based care delivery moved past the policy question that asked whether US healthcare should include PAs. A new era of research questions began, asking how PAs should be best used. This new era of research can be categorized as

  • clinical role delineation, particularly in a team setting
  • outcomes associated with PA care delivery
  • evaluations of the supply versus demand for PAs.

Multiple specialties in internal medicine and surgery developed team models that used PAs to address specific delivery issues. In an attempt to shorten ED length of stay, one urban medical center developed a discharge facilitator team with a physician, PA, and nurse to identify low-acuity patients who could be rapidly treated, resulting in a 35% shorter length of stay.83 To reduce 30-day readmission rates, another group found significant improvement using a PA home care program for patients recovering from cardiac surgery.84 A study at an academic cancer center described the development of a PA in infectious diseases to work on a multidisciplinary cancer team.85 Another evaluated the effect of including PAs or NPs in cardiology clinics. This study found that clinics with two or more PAs or NPs did at least as good, if not better at delivering guideline-recommended heart failure care than did physician-only clinics.86 At the same time, some studies did not provide sufficient information about the team design to allow for replication of the model. In particular, it was often unclear if the PA was strictly dedicated to the tasks described, or if part of the position included other clinical duties.

At the same time, PA role delineation studies were undertaken in a variety of specialties. For example, a study using the American Academy of Dermatology practice profile survey in 2006 identified that the 29% of participating practices employed PAs (23%) or NPs (10%), or both (6%) with most clinics using PAs or NPs to see medical dermatology patients while the physician was engaged in surgical and cosmetic dermatology.87 A case study of PAs and NPs in pediatric neurosurgery qualitatively described clinical, quality improvement, research, and teaching activities as well as scope of practice.88 Multiple studies involved surveying PAs in a given specialty to determine which clinical activities were performed.89-92 Other studies used large national data sets, such as the National Hospital Ambulatory Medical Care Survey, to identify types of services provided by PAs and NPs.93

One of the comprehensive role delineation analyses was a national, mixed-methods study of PAs in rheumatology. The study found that these specialized PAs worked in a range of practice types, treated a full range of rheumatology conditions, performed a variety of services, and often participated in research.94 Given the expansion of PAs into specialties, role delineation studies are critical and surprisingly absent from the literature. To understand the role of a PA in a given setting is to outline the range of tasks and competencies. More importantly, roles are defined by the division of labor between a PA and the other clinicians on the immediate team. Only one study to date has described roles, in primary care, in this manner.95

The number of studies evaluating the outcomes associated with PA practice is growing and more critical questions are emerging. Quality of care continues to be evaluated in various specialties and settings. Several studies demonstrated that enjoining PAs on hospitalists' services resulted in quality outcomes (such as length of stay, inpatient mortality, rehospitalization rates, and cost of service) that were at least as good as or better than teams including physician residents.96-98 Critical care studies also demonstrated that patients on services with PAs had similar mortality as patients on services with house officers.99 A particularly notable study demonstrated that PAs, NPs, and physicians provide similar amounts of low-value health services.100 Cost and efficiency studies are remarkable in consistently showing value added when a PA is introduced to the service. One Medicare study of patients who saw PAs for a large portion of their office visits had fewer visits per year, suggesting that PAs are less likely to refer than physicians.101 Several studies suggested that PAs could help healthcare organizations achieve cost savings.102,103 However, even within a specialty, PAs can perform a variety of roles that improve the throughput of patient care.104 Only one study compared the effectiveness of different roles in a specialty or setting.105

Quality of care and patterns of practice are emerging as important linked services when patient level outcomes and service use is examined. When undertaken in primary care settings just in this decade, the indicators are statistically indistinguishable from physicians and in some instances better.106


The PA profession continues to evolve, resulting in a greater need for research to improve understanding of how PAs fit into the healthcare landscape. Are they valued due to their reduced labor cost or is there some synergy effect that improves with team-based care? To address the growing array of societal questions, one strategy is for the profession to develop academically, and specifically develop a sufficient cadre of skilled researchers.107 Understanding the effects of PAs on any healthcare system requires measurement, development, team-based role definitions, and outcomes research. Better measures can be developed for concepts key to PA practice including autonomy and interdependence. Roles, in all medical and surgical specialties, need to be conceptually and operationally defined in relation to other team member roles, and evaluated on the organization and patient levels. Finally, studies must evaluate a variety of roles and multiple key outcomes simultaneously and longitudinally to truly understand how PA practice affects patients, providers, and organizations. Such studies require significant resources and advanced methodologies—which means if PAs want to study themselves, they will need research training and mentorship.


In the first half-century, research about PAs has reflected the context of the country. The profession was born in the 1960s, a complex time in US history when many people believed that social problems could be solved with enough effort and talent, and that in the end healthcare would be advanced. Such pursuit of social engineering created the PA profession and pushed it forward. Scientists examining many aspects of the nascent PA profession in the first era concluded that PAs were useful. The second era determined that PAs served society well. Entering the new millennium, the outcomes and contributions of the previous eras functioned as foundations for more refined and granular examination. The past generates the general direction but the scholars arising from within and outside the profession define where the profession is heading in terms of usefulness. In the next era, the focus needs to be on role delineation research in a wide range of specialties, critical team and organizational research, education processes, and outcomes of care including access, quality and cost of care, and workforce supply and demand. PA scholars are needed to be key players in asking and answering these questions. To do so requires the profession to invest in developing researchers. The future of PA research will be what the PA profession, collectively, makes it.


1. Ballweg RM, Hooker RS. Observations on the global spread of physician assistant education. J Physician Assist Educ. In press.
2. Hudson CL. Expansion of medical professional services with nonprofessional personnel. JAMA. 1961;176:839–841.
3. Gifford JF Jr., Prototype PA (Amos Johnson and Henry Treadwell). N C Med J. 1987;48(11):601–603.
4. Rosinski EF. Education and role of the physician. A redefinition. JAMA. 1972;222(4):473–475.
5. Rosinski EF, Spencer FJ. The training and duties of the medical auxiliary known as the assistant medical officer. Am J Public Health Nations Health. 1967;57(9):1663–1669.
6. Cawley JF, Cawthon E, Hooker RS. Origins of the physician assistant movement in the United States. JAAPA. 2012;25(12):36–42.
7. Hooker RS, Cawthon EA. The 1965 White House Conference on Health: inspiring the physician assistant movement. JAAPA. 2015;28(10):46–51.
8. Stead EA Jr. Conserving costly talents—providing physicians' new assistants. JAMA. 1966;198(10):1108–1109.
9. Stead EA Jr. The Duke plan for physician's assistants. Med Times. 1967;95(1):40–48.
10. Stead EA Jr. A college-based physician's assistant program. Med Times. 1968;96(8):847–850.
11. Stead EA Jr. Educational programs and manpower. Bull N Y Acad Med. 1968;44(2):204–213.
12. Stead EA Jr. The physician's assistant—job description and licensing. Med Times. 1969;97(8):246–247.
13. Stead EA Jr. Use of physicians' assistants in the delivery of medical care. Annu Rev Med. 1971;22:273–282.
14. Stead EA Jr. A new way of making doctors. Distance learning for non-traditional students. N C Med J. 2001;62(6):326–327.
15. Estes EH Jr. The critical shortage—physicians and supporting personnel. Ann Intern Med. 1968;69(5):957–962.
16. Estes EH Jr. The Duke Physician Assistant Program: a progress report. Arch Environ Health. 1968;17(5):690–691.
17. Estes EH Jr. Training doctors for the future: lessons from 25 years of physician assistant education. In: Clawson DK, Osterweis M, eds. The Roles of Physician Assistants and Nurse Practitioners in Primary Care. Washington, DC: Association of Academic Health Centers; 1993.
18. Glicken AD, Merenstein G, Arthur MS. The child health associate physician assistant program—an enduring educational model addressing the needs of families and children. J Physician Assist Educ. 2007;18(3):24–29.
19. Smith RA. Medex; a demonstration program in primary medical care. Northwest Med. 1969;68(11):1023–1030.
20. Fasser CE, Andrus P, Smith Q. Certification, registration and licensure of physician assistants. In: Carter RD, Perry HB III, eds. Alternatives in Health Care Delivery. St. Louis, MO: Warren H. Green; 1984.
21. Myers HC. The Physician's Assistant: A Baccalaureate Curriculum. Philippi, WV: Alderson-Broaddus College; 1978.
22. Estes EH Jr, Howard DR. The physician's assistant in the university center. Ann N Y Acad Sci. 1969;166(3):903–910.
23. Estes EH Jr, Howard DR. Potential for newer classes of personnel: experiences of the Duke physician's assistant program. J Med Educ. 1970;45(3):149–155.
24. Howard DR. The physician's assistant. One approach to the medical manpower problem. J Kans Med Soc. 1969;70(10):411–416.
25. Howard PL. PA clinical analyst and researcher find nonclinical jobs rewarding. AAPA News. 2000;21:4–10.
    26. Howard PL. Beyond the clinic: PAs in forensic medicine. AAPA News. 2000;12(21):1,10,11.
      27. Smith R. The medical assistant. Discussion on assurance of quality, competence and accountability. Public Health Pap. 1974;(60):142–152.
      28. Smith RA. Manpower and Primary Health Care: Guidelines for Improving/Expanding Health Services Coverage in Developing Countries. Honolulu, HI: The University Press of Hawaii; 1978.
        29. Smith RA, Bassett GR, Markarian CA, et al. A strategy for health manpower. Reflections on an experience called MEDEX. JAMA. 1971;217(10):1362–1367.
        30. Hooker RS. A cost analysis of physician assistants in primary care. JAAPA. 2002;15(11):39–50.
        31. Record JC, Greenlick MR. New health professionals and the physician role: a hypothesis from Kaiser experience. Public Health Rep. 1975;90(3):241–246.
        32. Pondy LR, Jones JM, Braun JA. Utilization and productivity of the Duke physician's associate. Socio-economic Planning Sciences. 1973;7(4):327–352.
        33. Miles DL, Rushing WA. A study of physicians' assistants in a rural setting. Med Care. 1976;14(12):987–995.
        34. Henry RA. Evaluation of physician's assistants in Gilchrist County, Florida. Public Health Rep. 1974;89(5):428–432.
          35. Riess J, Lawrence D. Practitioners in remote practices: summary of a study of training, utilization, financing and provider satisfaction. Washington, DC: Department of Health, Education and Welfare, Division of Medicine, Bureau of Health Manpower. 1976.
            36. Ekwo E, Daniels M, Oliver D, Fethke C. The physician assistant in rural primary care practices: physician assistant activities and physician supervision at satellite and non-satellite practice sites. Med Care. 1979;17(8):787–795.
            37. Record JC, Schweitzer SO. Staffing primary care in 1990—potential effects on staffing and costs: estimates from the model. Springer Ser Health Care Soc. 1981;6:87–114.
            38. Weiner JP, Steinwachs DM, Williamson JW. Nurse practitioner and physician assistant practices in three HMOs: implications for future US health manpower needs. Am J Public Health. 1986;76(5):507–511.
            39. Record JC, McCally M, Schweitzer SO, et al. New health professions after a decade and a half: delegation, productivity and costs in primary care. J Health Polit Policy Law. 1980;5(3):470–497.
            40. Schneider DP, Foley WJ. A systems analysis of the impact of physician extenders on medical cost and manpower requirements. Med Care. 1977;15(4):277–297.
            41. US Congress Office of Technology Assessment. Nurse practitioners, physician assistants, and certified nurse-midwives: a policy analysis (health technology case study 37), OTA-HCS-37. Washington, DC: US Government Printing Office; December 1986.
            42. Greenfield S, Komaroff AL, Pass TM, Anderson H, Nessim S. Efficiency and cost of primary care by nurses and physician assistants. N Engl J Med. 1978;298(6):305–309.
            43. Romm J, Berkowitz A, Cahn MA, et al. The physician extender reimbursement experiment. J Ambul Care Manage. 1979;2(2):1–12.
            44. Record JC, McCally M, Schweitzer SO, et al. New health professions after a decade and a half: delegation, productivity and costs in primary care. J Health Polit Policy Law. 1980;5(3):470–497.
            45. Scheffler RM. The productivity of new health practitioners: physician assistants and Medex. Res Health Econ. 1979;1(1):37–56.
            46. McCarty JE, Stuetzer LJ, Somers JE. Physician assistant program accreditation—history in the making. Perspective on Physician Assistant Education. 2001;12(1):24–38.
            47. Peterson SE, Rodin AE. GMENAC report on U.S. physician manpower policies: recommendations and reactions. Health Policy Educ. 1983;3(4):337–349.
            48. Cawley JF. The GMENAC report and the PA profession. JAAPA. 2016;29(10):49–52.
            49. Simon A, Link M, Miko A. Thirteenth Annual Report on Physician Assistant Educational Programs in the United States, 1996-97. Association of Physician Assistant Programs, May 1997.
            50. Oliver D, Baker J, Donahue W. First Annual Report on Physician Assistant Educational Programs in the United States, 1984-85. Alexandria, VA: Association of Physician Assistant Programs; 1985.
            51. Oliver D, Conboy J, Donahue W, McKelvey P. Survey of physician's assistant programs in the United States. J Med Educ. 1986;61(9 Pt 1):757–760.
            52. Physician Assistant Education Association. By the numbers: program report 31. Washington, DC, 2016. doi:10.17538/PS31.2016
            53. Perry HB, Fisher DW. The physician's assistant profession: results of a 1978 survey of graduates. J Med Educ. 1981;56(10):839–845.
            54. American Academy of Physician Assistants. AAPA Annual Census Survey of PAs. Accessed March 13, 2017.
            55. Johnson RE, Hooker RS, Freeborn DK. The future role of physician assistants in prepaid group practice health maintenance organizations. JAAPA. 1988;1(2):88–90.
            56. Johnson RE, Freeborn DK. Comparing HMO physicians' attitudes towards NPs and PAs. Nurse Pract. 1986;11(1):39,43-46,49.
            57. Carter RD, Oliver DR. An analysis of salaries for clinically active physician assistants. Physician Assist. 1983;7(7):14–16,19,23-24.
            58. Oliver DR, Carter RD, Conboy JE. Medical practice revenue and salaries of physician assistants. Physician Assist. 1985;9(5):138,143-144,149.
            59. Oliver DR, Carter RD, Conboy JE. Practice characteristics of male and female physician assistants. Am J Public Health. 1984;74(12):1398–1400.
            60. Kane RL, Olsen DM, Wilson WM, et al. Adding a Medex to the medical mix: an evaluation. Med Care. 1976;14(12):996–1003.
            61. Oliver D, Conboy J, Preston M. A comparison between the performances of medical students and physician's assistant students in interdisciplinary courses. J Med Educ. 1985;60(12):946–948.
            62. Cawley JF, Hooker RS. The effects of resident work hour restrictions on physician assistant hospital utilization. J Physician Assist Educ. 2006;17(3):41–43.
            63. Jones PE, Cawley JF, Capozzi LM. Gauging the publication productivity of PA faculty. JAAPA. 1997;10(1):51.
            64. Hegmann T, Dehn R. Publication productivity of PA faculty. Paper presented at: APAP Education Forum; November 7, 2002; Miami, FL.
            65. McDowell L, Clemens D, Frosch D. Analysis of physician assistant program performance on the PANCE based on degree granted, length of curriculum, and duration of accreditation. Perspectives Physician Assist Educ. 1999;10(4):180–184.
            66. Hooker RS, Hess B, Cipher D. A comparison of physician assistant programs by national certification examination scores. Perspectives Physician Assist Educ. 2002;13(2):81–86.
            67. Asprey D, Dehn R, Kreiter C. The impact of program characteristics on the physician assistant national certifying examinations scores. Perspectives Physician Assist Educ. 2004;15(1):33–37.
              68. Asprey D, Dehn R, Kreiter C. The impact of age and gender on the physician assistant national certifying examination scores and pass rates. Perspectives Physician Assistant Educ. 2004;15(1):38–41.
              69. Polansky M. A historical perspective on postgraduate physician assistant education and the association of postgraduate physician assistant programs. J Physician Assist Educ. 2007;18(3):100–108.
              70. HR 2015. Balanced Budget Act of 1997. 105th Congress (1997-1998). Accessed March 3, 2017.
              71. Simon A, Link M. Twenty-First Annual Report on Physician Assistant Educational Programs in the United States, 2004-2005. Association of Physician Assistant Programs, September 2005.
              72. Everett CM, Cawley JF, Hooker RS. Physician assistants in primary care. In: Hooker RS, Cawley JF, Everett CM, eds. Physician Assistants: Policy & Practice. 4th ed. Philadelphia, PA: F.A. Davis; 2017.
              73. Brock DM, Nicholson JG, Hooker RS. Physician assistant and nurse practitioner malpractice trends. Med Care Res Rev. [e-pub 25 July, 2016]
              74. Hooker RS, Nicholson JG, Le T. Does the employment of physician assistants and nurse practitioners Increase liability. J Medical Licensure Discipline. 2009;95(2):6–16.
              75. Grumbach K, Hart LG, Mertz E, et al. Who is caring for the underserved? A comparison of primary care physicians and nonphysician clinicians in California and Washington. Ann Fam Med. 2003;1(2):97–104.
              76. Berwick DM, Nolan TW, Whittington J. The triple aim: care, health, and cost. Health Aff (Millwood). 2008;27(3):759–769.
              77. OECD. Health at a Glance 2013: OECD Indicators.;jsessionid=18e9i4421x87.x-oecd-live-03. Accessed March 13, 2017.
              78. Dall TM, Gallo PD, Chakrabarti R, et al. An aging population and growing disease burden will require a large and specialized health care workforce by 2025. Health Aff (Millwood). 2013;32(11):2013–2020.
              79. Bodenheimer T, Pham HH. Primary care: current problems and proposed solutions. Health Aff (Millwood). 2010;29(5):799–805.
              80. Kimball AB, Resneck JS Jr. The US dermatology workforce: a specialty remains in shortage. J Am Acad Dermatol. 2008;59(5):741–745.
              81. Dorn SD. Mid-level providers in gastroenterology. Am J Gastroenterol. 2010;105(2):246–251.
              82. Adornato BT, Drogan O, Thoresen P, et al. The practice of neurology, 2000–2010: report of the AAN Member Research Subcommittee. Neurology. 2011;77(21):1921–1928.
              83. Sharma R, Mulcare MR, Graetz R, et al. Improving front-end flow in an urban academic medical center emergency department: the emergency department discharge facilitator team. J Urban Health. 2013;90(3):406–411.
              84. Nabagiez JP, Shariff MA, Khan MA, et al. Physician assistant home visit program to reduce hospital readmissions. J Thoracic Cardiovasc Surg. 2013;145(1):225–233.
              85. White CN, Borchardt RA, Mabry ML, et al. Multidisciplinary cancer care: development of an infectious diseases physician assistant workforce at a comprehensive cancer center. J Oncol Pract. 2010;6(6):e31–e34.
              86. Albert NM, Fonarow GC, Yancy CW, et al. Outpatient cardiology practices with advanced practice nurses and physician assistants provide similar delivery of recommended therapies (Findings from IMPROVE HF). Am J Cardiol. 2010;105(12):1773–1779.
              87. Resneck JS Jr, Kimball AB. Who else is providing care in dermatology practices? Trends in the use of nonphysician clinicians. J Am Acad Dermatol. 2008;58(2):211–216.
              88. James HE, MacGregor TL, Postlethwait RA, et al. Advanced registered nurse practitioners and physician assistants in the practice of pediatric neurosurgery: a clinical report. Pediatr Neurosurg. 2011;47(5):359–363.
              89. Larson EH, Coerver DA, Wick KH, Ballweg RA. Physician assistants in orthopedic practice. A national study. J Allied Health. 2011;40(4):174–180.
              90. Hinkel JM, Vandergrift JL, Perkel SJ, et al. Practice and productivity of physician assistants and nurse practitioners in outpatient oncology clinics at National Comprehensive Cancer Network institutions. J Oncol Pract. 2010;6(4):182–187.
              91. Ross AC, Polansky MN, Parker PA, Palmer JL. Understanding the role of physician assistants in oncology. J Oncol Pract. 2010;6(1):26–30.
              92. Chalupa RL, Hooker RS. The education, role, distribution, and compensation of physician assistants in orthopedic surgery. JAAPA. 2016;29(5):1–7.
              93. Hooker RS, Benitez JA, Coplan BH, Dehn RW. Ambulatory and chronic disease care by physician assistants and nurse practitioners. J Ambul Care Manage. 2013;36(4):293–301.
              94. Hooker RS, Rangan BV. Role delineation of rheumatology physician assistants. J Clin Rheumatol. 2008;14(4):202–205.
              95. Everett CM, Thorpe CT, Palta M, et al. Division of primary care services between physicians, physician assistants, and nurse practitioners for older patients with diabetes. Med Care Res Rev. 2013;70(5):531–541.
              96. Roy CL, Liang CL, Lund M, et al. Implementation of a physician assistant/hospitalist service in an academic medical center: impact on efficiency and patient outcomes. J Hosp Med. 2008;3(5):361–368.
              97. Dhuper S, Choksi S. Replacing an academic internal medicine residency program with a physician assistant—hospitalist model: a comparative analysis study. Am J Med Qual. 2009;24(2):132–139.
              98. Singh S, Fletcher KE, Schapira MM, et al. A comparison of outcomes of general medical inpatient care provided by a hospitalist-physician assistant model vs a traditional resident-based model. J Hosp Med. 2011;6(3):122–130.
              99. Costa DK, Wallace DJ, Barnato AE, Kahn JM. Nurse practitioner/physician assistant staffing and critical care mortality. Chest. 2014;146(6):1566–1573.
              100. Mafi JN, Wee CC, Davis RB, Landon BE. Comparing use of low-value health care services among US advanced practice clinicians and physicians providing value: advanced practice clinicians versus physicians. Ann Intern Med. 2016;165(4):237–244.
              101. Morgan PA, Shah ND, Kaufman JS, Albanese MA. Impact of physician assistant care on office visit resource use in the United States. Health Serv Res. 2008;43(5 Pt 2):1906–1922.
              102. Anderson TJ, Althausen PL. The role of dedicated musculoskeletal urgent care centers in reducing cost and improving access to orthopaedic care. J Orthop Trauma. 2016;30(suppl 5):S3–S6.
              103. Resnick CM, Daniels KM, Flath-Sporn SJ, et al. Physician assistants improve efficiency and decrease costs in outpatient oral and maxillofacial surgery. J Oral Maxillofac Surg. 2016;74(11):2128–2135.
              104. Everett CM, Thorpe CT, Palta M, et al. The roles of primary care PAs and NPs caring for older adults with diabetes. JAAPA. 2014;27(4):45–49.
              105. Everett C, Thorpe C, Palta M, et al. Physician assistants and nurse practitioners perform effective roles on teams caring for Medicare patients with diabetes. Health Aff (Millwood). 2013;32(11):1942–1948.
              106. Kurtzman ET, Barnow BS. A comparison of nurse practitioners, physician assistants, and primary care physicians' patterns of practice and quality of care in health centers. Med Care. [e-pub Feb. 23, 2017]
              107. Cawley JF, Ritsema TS. Where are the PA researchers. JAAPA. 2013;26(5):13,22.
              108. Pericoyianni-Paleologou H. The officier de santé in 19th-century France. JAAPA. In press.
                109. Sidel VW. Feldshers and “feldsherism.” The role and training of the feldsher in the USSR. N Engl J Med. 1968;278(17):934–939.
                110. Storey PB. The Soviet Feldsher as a Physician's Assistant. Washington, DC: National Institutes of Health; 1972.
                  111. Ettinger LE. Nurse-Midwifery: The Birth of a New American Profession. Columbus, OH: Ohio State University Press; 2006.
                    112. Witmer A, Seifer SD, Finocchio L, et al. Community health workers: integral members of the health care work force. Am J Public Health. 1995;85(8 Pt 1):1055–1058.
                    113. Anderson JG. Health care in the People's Republic of China: a blend of traditional and modern. Central Issues in Anthropology. 1992;10(1):67–75.
                    114. Maier CB, Aiken LH. Task shifting from physicians to nurses in primary care in 39 countries: a cross-country comparative study. Eur J Public Health. 2016:26(6):927–934.
                    115. Pedersen DM, Pedersen KJ, Santitamrongpan V. The Burmese medic: an international physician assistant analogue. J Physician Assist Educ. 2012;23(3):51–55.
                    116. Pedersen DM, Pedersen KJ, Barker DS. Rainforest physician assistants—the Papua New Guinea health extension officer: an international physician assistant analogue. J Physician Assist Educ. 2015;26(3):155–158.
                    117. Strand J. The practicante: Puerto Rico physician assistant prototype. J Physician Assist Educ. 2006;17(2):60–62.
                    118. Dever GJ. An alternative physician training program in the Pacific. Pacific Health Dialog. 1994;1(1):71–73.
                      119. Acuña HR. The physician's assistant and extension of health services. Bull Pan Am Health Organ. 1977;11(3):189–194.
                      120. Carlson D, Hamilton M. A midterm evaluation report of the rural health system project of the Ministry of Health Guyana. USAID AID/DSPE-C-0053. April 10, 1984.
                        121. Bergström S. Training non-physician mid-level providers of care (associate clinicians) to perform caesarean sections in low-income countries. Best Pract Res Clin Obstet Gynaecol. 2015;29(8):1092–1101.
                        122. Cobb N, Mechel M, Mulitalo K, et al. Findings from a survey of an uncategorized cadre of clinicians in 46 countries—increasing access to medical care with a focus on regional needs since the 17th century. World Health Population. 2015;16(1):72–86.
                          123. Mullan F, Frehywot S. Non-physician clinicians in 47 sub-Saharan African countries. Lancet. 2007;370(9605):2158–2163.
                          124. Buchan J, Perfilieva G. Making progress towards health workforce sustainability in the WHO European region. World Health Organization, 2015.
                            125. Eyal N, Cancedda C, Kyamanywa P, Hurst SA. Non-physician clinicians in sub-Saharan Africa and the evolving role of physicians. Int J Health Policy Manag. 2015;5(3):149–153.

                              PA; physician assistant; healthcare delivery; behavior; task transfer; team-based care

                              Copyright © 2017 American Academy of Physician Assistants