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A recent study by the Association of American Medical Colleges projects a shortage of between 17,800 and 48,000 primary care physicians by 2034. A December 2021 survey found that one in three physicians and advanced practice registered nurses intends to reduce their work hours, and one in five physicians plans to retire.

By sheer number, the shortage is projected to be the worst in California, Texas, and Florida. Making matters worse, graduates of U.S. and Canadian medical schools must complete at least one year of residency after graduation and pass Step 3 of the standardized U.S. Medical Licensing Exam to get a license to practice as a nonspecialist general practitioner, yet the number of medical school graduates exceeds the number of residency positions. Many graduates are stuck in limbo: They can neither apply the knowledge they acquired in school, nor hone and develop those skills in a residency program.


Some states are implementing innovative ways to help address the shortage. Missouri, a state with a large, medically underserved rural population, is the first state to launch a new licensure category of assistant physician (AP), not to be confused with physician assistant (PA). Assistant physicians are, in short, apprentice physicians, a common way to train physicians before the modern era of residency programs.

Missouri’s law permits assistant physicians to practice primary care in rural and underserved areas of the state with limited supervision by a licensed physician, with whom they must have signed a collaborative practice agreement. The Missouri Board of Registration for the Healing Arts began accepting assistant physician applications in January 2017. Applicants must submit letters of recommendation, proof that they graduated from an accredited medical school, and their exam scores from Step 1 and Step 2 of the three-step U.S. Medical Licensing Exam — the same requirements for admission into residency programs.

The law has already started lessening the primary care shortage. Missouri had 10,060 fully licensed primary care physicians engaged in direct patient care as of January 2023. As of mid-February 2023, the Missouri Division of Professional Registration listed 292 licensed APs, suggesting that assistant physicians increased the number of primary care physicians in Missouri by nearly 3 percent.


In a recently released Cato Institute briefing paper, Spencer Pratt and I provide an overview of how states are adopting this innovative approach to improving access to primary health care services.

Six other states have since passed laws similar to Missouri’s: Arkansas, Kansas, Utah, Arizona, Louisiana, and Idaho. And as this was written, Tennessee lawmakers sent an assistant physicians bill to the governor’s desk. Arkansas law refers to assistant physicians as “graduate registered physicians,” and Utah calls them “associate physicians.” Louisiana and Idaho use the term “bridge physicians” because their laws aim to help graduates bridge the waiting gap from graduation until they get another chance to apply for a residency position. Tennessee lawmakers call them “graduate physicians.”

Whatever name they go by, states typically require assistant physicians to sign an agreement with a fully licensed physician who can bill third-party payers for their services. All states require third-party payers to pay for assistant physician services at the same rate as physician assistants.

Supervising physicians need not be present when assistant physicians are providing services. Assistant physicians in Missouri can renew their licenses indefinitely. The other states limit the number of years assistant physicians may serve patients, after which they are expected to have obtained a position in an accredited residency program.

If doctors don’t land a residency slot within a designated period, those states will block them from further practicing as assistant physicians. For example, Idaho’s bridge physician license is not renewable, while Louisiana allows bridge physicians to renew for two additional years.

The state of Washington recently enacted an assistant physician program, but only for international medical graduates who emigrate from other countries and want to care for patients — not for graduates of U.S. or Canadian medical schools. There is no good reason why states shouldn’t enable both international and domestic graduates to become assistant physicians.

In our briefing paper, we propose that states can innovate even further by enabling medical school graduates, including international medical graduates, to use their experience as assistant physicians as an alternative pathway to unrestricted licensure as general practitioners. If one or two years of residency plus passing Step 3 of the U.S. Medical Licensing Exam qualifies physicians in most states to practice medicine as general practitioners, then three or more years of experience as an AP and passing the same exam should suffice.

If states lift constraints and allow domestic and international medical school graduates to become assistant physicians and use their experience as an independent pathway to general medical practice, they can increase the number and variety of primary care providers and improve access to primary care while reducing cost.

Jeffrey A. Singer, M.D., practices general surgery in Phoenix, Arizona, and is a senior fellow at the Cato Institute.

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