Roles of Nonphysician Clinicians as Autonomous Providers of Patient Care

IN RECENT years, nonphysician clinicians (NPCs) have provided increasing amounts of health care that, in the past, has been provided principally by physicians.^{1 - 9} Most of these NPCs are within 10 distinct medical/surgical disciplines that are the subject of this article. Three are the "traditional disciplines," which include nurse practitioners (NPs), certified nurse-midwives (CNMs), and physician assistants (PAs). Three others are "alternative" or "complementary" disciplines, including chiropractors, naturopaths, and practitioners of acupuncture and herbal medicine. The final 4 are specialty disciplines, including optometrists, podiatrists, certified registered nurse anesthetists (CRNAs), and clinical nurse specialists (CNSs).

Through statutes and regulations, states have granted practice prerogatives to NPCs in each of these disciplines. First among these prerogatives is licensure, which establishes their right to practice, although it does not assure their autonomy as practitioners. This latter prerogative is codified within state practice acts, which also delineate scope of practice and authorize prescriptive privileges. Other regulations, such as state insurance mandates and Medicare and Medicaid policies, affect reimbursement.

While statutes and regulations are not the only factors influencing the practices of NPCs, they are powerful determinants of their authority and independence.^{10 - 12} Therefore, it is not surprising that, in recent years, legislative actions have been the focus of an increasing amount of energy and activity.^{5 ,10 - 14} This study was undertaken to analyze the practice prerogatives that have been granted to NPCs through laws and regulations and to assess how these prerogatives are likely to shape their roles in clinical practice in the future.

The following 5 trends emerged from this analysis:

Taken together, these dynamics describe a workforce of NPCs that is growing in size, prerogatives, and participation. This presents a number of challenges to educators, regulators, and practitioners in the future. First, the roles and responsibilities of both physicians and NPCs will have to be redefined within the context of a diverse array of independent clinical disciplines. Second, the future magnitude of each discipline will have to be assessed in relation to others with overlapping skills and prerogatives. Third, future clinicians will have to be equipped not only with the knowledge and skills needed to provide their unique services but also with the ability to collaborate with a range of independent practitioners. And finally, future systems of health care will have to be organized and regulated in ways that assure that a pluralistic workforce of independent clinicians will be able to deliver a uniformly high quality of care.

Data were obtained from published reports issued by professional organizations in each of the 10 disciplines^{16 - 36} ; from analyses by independent organizations and individuals^{9 ,37 - 39} ; from the Health Policy Tracking Service at the National Conference of State Legislatures⁴⁰ ; and from the Internet Web sites of the individual states.⁴¹ Additional data were obtained from professional organizations by telephone contact or from their Internet Web sites (Table 1). Legislation concerning NPCs is an arena with considerable activity. The data reported herein report the status of NPC regulation as of July 1, 1998.

The NPC disciplines analyzed in this article exclude those engaged in mental health care services. The term advanced practice nurse (APN) refers to NPs, CNMs, CRNAs, and CNSs. The term physician services refers to services that replicate or substitute for the services normally provided by physicians. Although some states permit NPCs (other than APNs) to use titles such as "doctor" or "physician," and such titles are used as a matter of custom in other states, the term nonphysician has been applied to all of the disciplines analyzed in this article as a means of distinguishing them from the larger group of medical doctors and doctors of osteopathic medicine.

The responsibility for regulating the health care disciplines is vested in the 50 states and the District of Columbia. Although states often grant lesser forms of recognition, such as certification, registration, or approval to practice, licensure is preferred because it is more prestigious and because it facilitates the growth of practice prerogatives and access to reimbursement. For similar reasons, most disciplines have sought regulatory boards that are specific for their disciplines. There is a natural continuum that connects education, credentialing, licensure, and practice. Indeed scope-of-practice statutes often refer to the content of the educational experiences.

Training and Credentialing. Most practicing NPs hold graduate degrees, and almost all current training is at the master's degree level.^{4 ,16 ,34} NPs are principally trained in primary care, with special emphasis on areas such as adult health, pediatrics, family health, women's health, or gerontology, although 5% to 10% train in critical care, emergency care, and other specialty disciplines.³⁴ The training and credentialing of NPs build on their nursing education.^{4 - 6} Education includes wellness care and the management of acute and chronic illness across a broad spectrum of disease, with an emphasis on case management, counseling, and patient education. In contrast, the training of CNMs is more narrowly focused, including antepartum, intrapartum, and postpartum care, gynecology, and family planning.²² PAs also are trained as primary care providers, although approximately half subsequently serve in specialty roles.^{7 - 8 ,35 - 36} Their training and credentialing are centered on the clinical encounter in both ambulatory and inpatient settings, and they cover a wide spectrum of disease.

Licensure. NPs and CNMs receive dual recognition. They derive primary recognition as registered nurses in all states and secondary recognition in their advanced disciplines in every state except Illinois, in which legislation that will provide recognition is pending (Table 2).^{22 ,37} Similarly, all jurisdictions except Mississippi recognize PAs.^{31 - 32} While licensure is common, more limited forms of recognition are applied in many states. A few states have established boards specific to NPs and CNMs, but most regulate these disciplines through their boards of nursing or through combined boards of nursing and medicine (Table 2). In contrast, PAs are governed predominantly by boards of medicine.

Autonomy. The degree to which traditional NPCs may practice independent of physician supervision or delegation varies considerably among the states (Table 2). NPs have independent practice authority in 21 states, although in 2 of these states the degree of independence is separately determined for each individual practitioner.^{13 - 14 ,37} In other states, their practice authority is contingent on physician delegation or oversight. However, the direct involvement of the delegating physician may be at intervals extending from a few days to 2 weeks, and only 2 states require that a physician be physically present. CNMs have a similar degree of independence, although most states require that CNMs maintain a relationship with an obstetrician. However, 6 states mandate direct access to CNMs, independent of any requirement.²² In contrast, PAs practice with physician direction and within the scope of practice of the supervising physician, as with NPs, this supervision may be intermittent and at a distance, and the autonomy of PAs may be substantial.^{13 ,31 - 32}

Scope of Practice. Most states permit NPs, PAs, and CNMs to perform physical examinations and make a diagnoses throughout the range of disease and dysfunction that falls within their training and expertise (Table 3).^{4 - 8 ,13 - 14 ,22 ,31} They also are given broad latitude in ordering and interpreting laboratory tests and x-ray films, performing venipunctures and immunizations, suturing wounds, and doing some invasive procedures, such as lumbar punctures and joint aspirations, and some allow them to make death pronouncements. In addition, CNMs are permitted to care for normal pregnancies and perform normal deliveries in all states, to perform simple episiotomies and provide nonpregnant gynecological care in most states, and to care for complicated pregnancies in many states.

Prescriptive Authority. Prescriptive authority varies widely among practitioners of the traditional disciplines (Table 3).^{22 ,31 ,37} NPs and CNMs have no prescriptive authority in Illinois, a state that does not recognize them as distinct disciplines. They are limited to prescribing noncontrolled drugs under physician supervision in one third of the states and further limited to dispensing these drugs under physician orders in 2 states. However, in the other 60% of the states, NPs and CNMs have the authority to prescribe controlled substances, although the permitted schedules vary, and some states impose limitations on the duration of prescriptions. Twelve states have granted NPs and CNMs the authority to prescribe controlled drugs independent of physician involvement.

The pattern of prescriptive privileges for PAs is similar to that of NPs and CNMs. PAs lack prescriptive authority in 8 states, and they are limited to prescribing noncontrolled drugs in another 9 jurisdictions. The remaining 34 states allow them to prescribe controlled drugs of varying schedules and to do so independent of direct physician involvement, although this must be in the context of overall physician supervision and direction or within a defined protocol.

Training and Credentialing. The goal of chiropractic education, which spans 4 years, is to prepare chiropractors to be primary care providers who can serve as the portal of entry to the health care system, performing wellness care, general primary care, and musculoskeletal care.²⁰ They are expected to diagnose conditions and care for patients in health and disease and to consult with or refer to other health care providers when necessary. Chiropractic training concentrates on the physiology, diagnosis, and treatment of disorders attributable to the neuromusculoskeletal systems, with an emphasis on chiropractic technique. Although only 15% of their clinical training is specifically devoted to other organ systems, many disorders attributed by chiropractors to the neuromusculoskeletal system are considered by allopathic physicians to have a somatic basis.

Practitioners of acupuncture and herbal medicine also are trained to be the clinicians of first encounter. Their curriculum, which usually spans 3 years, prepares them to approach diagnosis from the Oriental perspective (look, smell, listen, and feel) and to treat pain, addiction, and a range of common problems with acupuncture and/or herbal remedies.^{1 ,9} Two thirds of patients who seek their care have musculoskeletal complaints, and a large number have headaches. Most others have fatigue, anxiety, depression, and related symptoms.⁴² It is likely that the future use of acupuncture will be influenced by the recent National Institutes of Health Consensus Conference, which concluded that acupuncture may be useful in treating postoperative and chemotherapy-induced nausea, menstrual cramps, headache, fibromyalgia, low-back pain, asthma, and other common disorders.⁴³

Naturopaths, like allopathic physicians, receive 4 years of postbaccalaureate education culminating in a doctoral degree.¹ They are broadly trained in the preclinical sciences and the clinical disciplines, with an emphasis on health promotion, disease prevention, and treatment based on the stimulation or support of natural processes. Their clinical education, which is entirely outpatient based, is designed to prepare them to be primary care providers. However, their scope of practice excludes many drugs and procedures that are commonly used by primary care physicians. Only Utah requires naturopaths to obtain an additional year of residency training, although graduates in other states often seek such training. Some naturopaths obtain added certification in acupuncture, traditional Chinese medicine, or midwifery.

Licensure. Chiropractors are licensed in all 51 jurisdictions, and they are regulated by separate boards in 48 jurisdictions (Table 2).¹⁹ However, practitioners of acupuncture and herbal medicine are licensed or otherwise recognized in only 34 states, although 3 others permit the practice of acupuncture under physician supervision; naturopaths are licensed in only 11 states.^{10 ,17 ,21} Both naturopaths and acupuncturists are less frequently governed by separate boards than are chiropractors (Table 2). In recent years, there has been a considerable legislative thrust to further expand the licensure of both acupuncture and naturopathy. Over the past 3 years, 6 states adopted licensure laws for acupuncture and 1 state licensed naturopathy.^{17 - 18 ,40} Moreover, during 1997 alone, the licensure of acupuncturists was considered in 4 additional states, several of which appear likely to grant approval, and the licensure of naturopaths was considered in 4 states.⁴⁰

Chiropractors are permitted to use titles such as doctor of chiropractic (DC) or chiropractic physician (CP) in most states, although 5 states restrict their title to chiropractor.¹⁹ Similarly, all states that license naturopaths consider them to be physicians and designate their titles as doctor of naturopathic medicine (ND) or naturopathic physician (NP).²¹ However, only 3 of the 34 states licensing acupuncturists permit practitioners to use the title of doctor and most require the title of acupuncturist.¹⁷ Indeed, a number of states specifically prohibit the use of doctor by acupuncturists unless they possess a doctoral degree.

Scope of Practice and Autonomy. All states allow practitioners in the 3 alternative disciplines to perform physical examinations and diagnose patients' conditions and, except for acupuncture, to perform venipunctures and order and interpret laboratory tests and x-ray films (Table 3).^{17 - 21} The scope of practice of all 3 disciplines gives them broad latitude to treat disease or physiologic dysfunction by means of manipulation, physiotherapy, electrotherapy, hydrotherapy, acupuncture, and natural and herbal remedies. Moreover, some states permit naturopaths or chiropractors to serve as "gatekeepers." Most states that license naturopaths also permit them to care for and deliver uncomplicated pregnancies and to provide care during complicated pregnancies, and all states allow them to provide nonpregnant gynecological care. In addition, two thirds of states allow naturopaths to suture wounds, perform minor invasive procedures, and inject nutrients. In general, these practices of alternative NPCs are independent of physician supervision or delegation. However, acupuncture is an exception, with one third of the states that license acupuncture requiring the involvement of a physician, dentist, or chiropractor (Table 2).

Prescriptive Privileges. Naturopathic physicians have the independent authority to prescribe noncontrolled drugs in 10 of the 11 states in which they are licensed, although in 4 they are limited to board formularies (Table 3).²¹ However, all 11 states permit them to prescribe and dispense minerals, herbal remedies, and food supplements. These latter prerogatives also are available to chiropractors in almost all states and to acupuncturists in more than half of the states in which they are licensed (Table 3). However, the prescriptive authority of chiropractors and acupuncturists is limited to natural products, and neither discipline has prescriptive authority for controlled drugs.

Optometrists. Optometrists' 4-year curriculum encompasses human biology, ocular biology, optics, disorders of the eye, and the ocular manifestations of systemic disease, and it trains them to be primary health care providers.²⁷ Optometrists are licensed or certified in all 51 jurisdictions, and, in all but 2, the boards governing them are specific for optometry (Table 2). In general, states do not designate the titles of "doctor" or "physician" for optometrists, although Arkansas does allow use of the title "optometric physician." However, "doctor" is commonly used in daily practice.

Optometrists have long had privileges that include examination of the eye, making a diagnosis, prescribing lenses and other vision devices, and removing superficial foreign bodies from the eye. They have prescriptive privileges in all states, but that authority is limited to topical medications in 21 (several of which permit them to prescribe oral analgesics). Only 4 states permit optometrists to administer drugs by injection. In recent years, 49 states have added privileges in therapeutic optometry, most after separate certification, and 35 of these allow optometrists to treat glaucoma.^{28 - 29} Oklahoma is the only state that currently allows optometrists to perform laser surgery, although this prerogative is being considered in several other states.

Podiatrists. Podiatric education, which also spans 4 years, includes anatomy (with an emphasis on the lower extremity), the preclinical sciences, and a range of information relevant to the treatment of diseases of the foot, including radiology, orthopedics, sports medicine, orthotics, trauma, anesthesia, operative technique, and podiatric surgery.²⁴ In addition, attention is given to a general understanding of systemic disease processes. Podiatrists are licensed or certified in all 51 jurisdictions and in 70% they are regulated by separate boards. Although only 6 states specifically allow the use of titles such as "podiatric physician," "podiatric surgeon," or "doctor of podiatric medicine," such titles are common in daily practice.²⁴

Podiatrists practice independently and exercise independent prescriptive authority in all 51 jurisdictions.²⁶ Historically, the privileges of podiatrists have centered on the diagnosis and treatment of disorders of the foot and ankle, including medical treatment, the use of prosthetic devices, and surgical treatment under local anesthesia. Other defined therapeutic privileges in many states include mechanical, manipulative, and electrical treatment. However, their range of practice extends to areas between the ankle and the knee in 29 states and to the upper muscles of the leg in 9 states. In addition, 10 states allow podiatrists to amputate toes, and 4 permit them to treat conditions in the hands that are also found in the feet.

Certified Registered Nurse Anesthetists and Certified Nurse Specialists. CRNAs and CNSs are separately licensed or otherwise recognized in most states (Table 2).^{30 ,37} However, 7 states consider them both to be registered nurses, and 8 others limit the separate recognition of CNSs to those engaged in psychiatric and mental health care practices. Both disciplines are governed principally by separate boards of nursing or by boards of nursing combined with boards of medicine.

CRNAs receive intensive training in anesthesia and pain management.³⁰ Their scope of practice includes the range of prerogatives necessary to treat pain and perform anesthesia in a manner similar to physicians. Currently, there are approximately equal numbers of CRNAs and anesthesiologists, but they differ in geographic distribution.¹⁵ In many smaller communities, CRNAs are the sole practitioners capable of administering anesthesia. However, they have the authority to practice independent of physicians in only 18 states (Table 2). While in most other states CRNAs are required to practice under the supervision of an anesthesiologist or surgeon, podiatrists and dentists are permitted to serve in this supervisory role in some states. The prescriptive authority of CRNAs also is limited and is usually contingent on some form of physician collaboration or delegation. However, in 9 states, CRNAs have the independent authority to prescribe controlled substances.

CNSs receive master's level training as nurse clinicians in single specialties.³⁴ Their scope of practice is defined by their training, certification, and experience. They have the authority to practice independently in 20 states but require collaboration with physicians in 24 and must be supervised by physicians in 7 (Table 2).³⁷ Their prescriptive authority also is more limited than that of other APNs. However, they do have independent prescriptive authority for controlled substances in 9 states.

For 3 decades, the reimbursement of NPs, CNMs, CNSs, and PAs by Medicare and Medicaid has been governed by the "incident to" provision, which allows NPCs who are employed by physicians to be reimbursed by means of payments to the employer. In 1977, the Rural Health Clinics Act permitted Medicare and Medicaid to directly reimburse NPs, PAs, and CNMs working in free-standing, physician-directed rural clinics located in health professions shortage areas (HPSAs). This subsequently was expanded to cover care provided at other locations, and on-site physician supervision was waived unless it was a requirement of the state. The Balanced Budget Act of 1997 further expanded direct Medicare reimbursement for NPs, PAs, and CNSs to include all nonhospital sites, and it removed any requirement for physician involvement (Table 4).⁴⁴ This represents a large step forward in achieving autonomy for these disciplines.

All but a few states reimburse traditional NPCs through Medicaid, but reimbursement rates vary from 50% to 100% of physician fees (Table 4).^{14 ,23 ,33 ,37} A federal mandate allows family and pediatric NPs and CNMs to bill Medicaid directly within the limits established by the state, if they are allowed to practice independently in that state. However, states have the option to cover fewer services and to require more physician supervision than included within their practice acts. NPs, PAs, and CNMs also are allowed to bill the Civilian Health and Medical Program of the Uniformed Services (CHAMPUS), the Federal Employees Health Benefits Program, and other federal programs.^{23 ,33 ,37} Thus, reimbursement is available for traditional NPCs from most governmental programs most of the time.

Among the alternative disciplines, chiropractors are allowed to bill Medicare, and new billing codes applicable to chiropractic procedures have facilitated this process (Table 4).²⁰ Chiropractors also are reimbursed for care provided under workers' compensation, and 26 states cover chiropractors under Medicaid. However, none of the governmental payers currently covers acupuncturists or naturopaths.

Optometrists and podiatrists are allowed to bill Medicare and Medicaid directly in a manner similar to physicians (Table 4).²⁵ CRNAs also are permitted to directly bill Medicare and other federal programs and, in 36 states, to directly bill Medicaid, although billing frequently is through the employer and often in the form of team billing with anesthesiologists.⁴⁵ The Health Care Financing Administration recently proposed that its long-standing requirement for physician supervision of CRNAs be removed.

The reimbursement of CNSs by Medicare and other federal programs follows the pattern established for NPs, including the recently enacted changes in Medicare, but reimbursement from CHAMPUS is available only for psychiatric CNSs.^{37 ,44} In 36 states, Medicaid reimbursement of CNSs also follows the pattern of NP reimbursement, but in the other 15 states CNSs are considered registered nurses for reimbursement purposes.

Many states have enacted legislation mandating that private health care plans include reimbursement for particular groups of NPCs (Table 4). Although most apply to all health care plans, some are limited to managed care organizations. These mandates are powerful elements in the growth and independence of NPCs. In addition, 16 states have enacted "any willing provider" (AWP) laws that, in general, prohibit health care plans from denying access to any licensed provider whose training and scope of practice include the services covered by the plan and who is willing to meet the terms and conditions of the plan.⁴⁰ Most AWP laws are broad in their definition of providers, although some cite specific disciplines. Washington's law, which is the most liberal, extends coverage to any licensed practitioner whose scope of practice encompasses the clinical conditions covered in the plan, irrespective of the mode of care offered, as long as it is safe. State courts have overturned the AWP law in Louisiana, based on conflicts with the Employee Retirement Insurance Security Act (ERISA), and have limited the law in Arkansas to plans not covered by ERISA, while Tennessee's law applies only to TennCare.

At the federal level, bills have been introduced into both the Senate and the House of Representatives that would mandate a vast expansion of the access of patients to NPCs. For example, the Access to Medical Treatment Act of 1997 would allow patients to receive any medical treatment they wanted and any method of treatment they requested. While none of these bills has been enacted, they are broadly endorsed by NPC professional organizations and are an expression of the will of a growing segment of the public.

While NPCs are authorized to provide a range of physician services, often in an independent manner, and to be reimbursed for that care, there is marked variation in their scope of practice, independence, and reimbursement. Similarly, the numbers of practicing NPCs vary substantially from state to state.¹⁵ In 1994, Sekscenski et al¹⁰ reported that for NPs, CNMs, and PAs there was a correlation between practitioner numbers and practice prerogatives in the various states. To further examine this relationship and determine whether it applies to other disciplines, the practice prerogatives of traditional and alternative NPCs were compared state by state with the numbers of these practitioners.

A system for scoring practice prerogatives was established for each of the 6 disciplines by assigning credit for licensure, separate state boards, scope of practice, prescriptive authority, autonomy, and access to reimbursement. PAs displayed the greatest homogeneity and the highest average scores. NPs presented a bimodal pattern, with the mode of highest scores being similar to that of PAs. The scores of CNMs displayed wide variation, but few were clustered in the highest range. Chiropractors and naturopaths followed the pattern of CNMs, with a wide distribution of scores and with most states clustered in the middle range. The 34 states that license acupuncture were the most variable in their scoring patterns. These data show not only the extreme variability of practice prerogatives that exists among the states but also the substantial prerogatives that NPCs have been granted in some of the states.

The numbers of practitioner in each state¹⁵ correlated with the practitioner prerogatives granted by that state. For all disciplines except naturopathy, the correlation coefficients varied from 0.43 to 0.60 and were statistically significant. These are similar to the results previously reported for NPs, CNMs, and PAs.¹⁰ A similar trend was observed for naturopathy (r=0.27), although it was not statistically significant.

Practice prerogatives were greatest in states that regulated NPCs through boards dedicated to their disciplines and least in states in which regulation was through the boards of medicine. Scores for NPs correlated with CNMs' scores (r=0.42) and more weakly with PA scores (r=0.33). Similarly, scores for naturopaths correlated with acupuncture scores (r=54). However chiropractic scores did not correlate with the scores of other NPCs, and there was no overall correlation between the scores of traditional and alternative NPCs.

Certain states tended to have either higher or lower scores for all disciplines, and they were clustered geographically. For example, scores for all NPCs tended to be higher in Alaska, Washington, Oregon, New Mexico, North Dakota, New Hampshire, and Maine. Conversely, scores tended to be lower in Alabama, Louisiana, Mississippi, Georgia, and South Carolina. Hawaii had a high score for acupuncture but low scores for all other disciplines. However, in most states there was no clear pattern of scores, suggesting that local factors within each discipline played a stronger role than the general acceptance or rejection of NPCs.

These data show that there are substantial opportunities to improve the practice environments for NPCs in many states, assuming that the standards to be attained are represented by those states with the highest scores. Moreover, the correlations reported above are consistent with the view that as these environments improve, the numbers of NPCs who will choose to train and practice there will increase.^{4 - 8 ,10} However, they may also indicate that as NPCs increase in numbers, they are better able to effect improvement in their practice environments. It is likely that both dynamics are operative. Indeed, they may reinforce each other.

There are several levels of clinical authority. The first level includes diagnosing the undifferentiated patient, communicating that diagnosis, and assuming the principal responsibility for care. These prerogatives, which are central to the practice authority of physicians, have been granted to NPCs under at least some circumstances in most states, and in many states they have been granted independent of direct physician involvement. This clinical authority is consistent with the training and credentialing that NPCs undergo. Each discipline undertakes to prepare its graduates to be clinicians of first contact, with skills to perform a history and physical examination, make a diagnosis, treat patients when possible, and refer to other clinicians when appropriate.

The second level of authority relates to the range of services provided. Each of the NPC disciplines provides a spectrum of services that, to varying degrees, overlaps those of physicians. Some NPCs practice independently, while others require physician supervision, delegation, or referral. Some care for patients with a wide range of disorders. Others are more narrowly focused. However, none participate throughout the entire range of care provided by the physicians whose services they overlap, and NPCs do not collectively span the entire breadth of physician services. Rather, their scope of practice and prescriptive privileges limit them to less complex levels of care that exclude much of the care customarily provided by physicians. The services they provide can be considered within the following 4 levels of care:

Simple Licensed General Care. This level includes wellness care and the care of uncomplicated or self-limited acute disorders and of mild chronic conditions. It encompasses more than half the care provided by primary care physicians^{7 - 8 ,46 - 49} and is the major area of independent care provided by the 6 traditional and alternative NPC disciplines.

Complex Licensed General Care. This level includes the care of patients with severe illness of an acute, chronic, or recurrent nature, often involving multisystem disease. It is a major part of the practice of primary care physicians and of some specialty physicians, but it is beyond the range of practice prerogatives granted to most NPCs.

Routine Licensed Specialty Care. This level includes the less complicated care provided by those clinicians who focus on specific groups of diseases, conditions, or technologies. It is the major domain of both specialty physicians and specialty NPCs (optometrists, podiatrists, CRNAs, and CNSs). It also engages some of the effort of primary care physicians and of NPs and PAs who have a specialty orientation.

Complex Licensed Specialty Care. This level includes the care that is usually restricted to physicians and generally requires the particular skills of specialty physicians.

Although there is considerable overlap between physicians and NPCs, the overlap is limited, and it is skewed to the less complex end of the clinical spectrum.⁶ However, a number of factors are likely to influence the extent of this overlap in the future.

NPC Supply. One factor influencing NPC involvement is the growing number of NPCs. From the analysis above, it appears that the number of NPCs within the various disciplines may be a determinant of the prerogatives available to them, and most NPC disciplines are growing at a significant rate.¹⁵ Growth is particularly rapid among the traditional and alternative disciplines, which are the major contributors of primary care. The total number of NPCs providing primary care will almost double over the next 10 years. The supply of specialty NPCs also will grow but at a lesser rate. However, their growth coincides with a further expansion in the number of specialty physicians and a general concern about the number of physicians overall.^{2 ,50 - 52} It is likely that continued increases in both the supply and prerogatives of NPCs will further deepen this concern.

Organization of Care. Another factor influencing the overlap of physicians and NPCs is the organization of care. For example, while caring for the whole patient has been the goal of medical care, defined tasks have become a prominent mode of care. This is true not only for specialty care, with its defined technical tasks, but also for primary care, in which urgent care has been separated from elective care and in which the responsibilities for preventive services, counseling, treatment, and follow-up have been distributed among various clinicians. Many routine tasks traditionally performed by physicians are now being performed independently by NPCs, and the range and technical complexity of such tasks is expanding. Examples include the increasing involvement of NPs and PAs in emergency care and optometrists in therapeutic eye care.^{28 ,53}

Market Dynamics. The growing participation of NPCs is also being fostered by new market dynamics. Provider organizations, such as clinics, physician group practices, and health maintenance organizations, are incorporating increasing numbers of NPCs into their practices or offering them opportunities to practice independently.^{49 ,54 - 55} In these settings, some NPCs acquire prerogatives that otherwise would not be available to them. In addition, increasing numbers of insurers are creating benefit plans that include NPCs, partially in response to state mandates but also in response to consumer demand. This access to reimbursement further enhances the independent participation of NPCs in clinical practice.

Displacement vs Supplementation. The growing numbers, increasing prerogatives, and expanding participation of NPCs will surely affect the demand for physicians, particularly those involved in simple licensed general care and routine licensed specialty care. However, the interrelationships between the demand for physicians and the availability of NPCs are complex. For example, while the need for physicians will be directly affected when NPs or naturopaths provide primary care, when CNMs perform deliveries, or when CRNAs administer anesthesia, services such as acupuncture, spinal manipulation, and herbal therapy may supplement rather than supplant the care provided by physicians. Counseling, patient education, and case management may also be adjunctive. However, it is likely that even these groups of services will decrease the demand for physicians, although they may not directly overlap the services that physicians provide.

Philosophy. Finally, in considering the overlapping care provided by physicians and NPCs, it should be recognized that important characteristics of that care differ because of philosophical differences among the disciplines. Thus, although PAs, optometrists, and podiatrists generally share with physicians the "medical model" of care, not all NPCs practice within that model. For example, NPs, CNMs, and CNSs care for patients within a "nursing model" that emphasizes prevention, case management, patient education, and counseling.^{4 - 6} Practitioners of acupuncture and herbal medicine provide care within the tradition of Chinese medicine, which emphasizes an empirical, holistic approach to prevention and the restoration of balance.⁴³ Chiropractic care is built around the "chiropractic encounter," which emphasizes physical contact with patients,²⁰ and naturopathy emphasizes the stimulation and support of natural processes. These different philosophical orientations lead to differences in both the characteristics and content of care for identical disorders, and they add complexity to any direct comparisons of the spectrum of services provided.

It seems clear from this and other analyses^{1 - 11} that NPCs are a growing force in clinical medicine. In some states, they are well established already, while in others certain disciplines are in their infancy. Their continued growth in numbers, prerogatives, and independence seems assured by a confluence of interests that includes health care organizations, insurers, legislators, physicians, and NPCs themselves. However, there is little uniformity among the NPC disciplines. Rather, each has its own curriculum, philosophy, and approaches to care and each practices within its own regulatory and clinical framework. Individually, each offers a consistent set of services, and the states have codified many of these within specific practice acts. However, collectively, this pluralistic array of providers lacks a unifying clinical principle, and their growing divergence in both regulatory oversight and clinical practice has the potential to further fragment the nation's health care system.

How are patients to choose from among physicians and various NPCs? How will legislators determine whether appropriate prerogatives are being granted to each? How can payers be assured that the overlapping prerogatives of physicians and NPCs will not create redundancies in both services and costs? And how will educators prepare this diverse array of disciplines to practice in a consolidated health care system? Earlier in this century Abraham Flexner confronted an analogous problem of heterogeneity and oversupply among physicians.⁵⁶ What followed was an effort to link education, regulation, and clinical practice within a single discipline. The circumstances are different today, but the requirements are no less. It is time for interdisciplinary regulation and clinical integration so that a health care workforce that includes a diversity of disciplines can be assured of providing a uniform level of care in the future.