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 After PAs gained initial credibility, historical documents emerged suggesting that prototype PAs were abundant in the world with different names, origins, and functions.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).
THE EARLY YEARS: 1960S TO EARLY 1980S
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
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
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
RETRENCHMENT AND DIVERSIFICATION: 1980S TO 2005
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
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?
CONTRIBUTION TO HEALTH SERVICES: 2005 TO PRESENT
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.
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