By Erica Cohen

American doctors can be trained in one of three different ways. Traditional (allopathic) medical schools grant M.D. degrees. Foreign medical schools also grant M.D. degrees but outside of the United States. And osteopathic medical schools grant D.O. degrees.

Osteopathic and allopathic medicine have very different philosophies about medical care. Osteopathic medicine focuses on the idea that all body systems are interrelated and dependent upon one another for good health. Osteopathic physicians use modern medicine to treat their patients, but they add manipulative medicine (OMM), a set of manual techniques to diagnose illness and injury and enhance the body's capacity to heal.

In 2008, there were approximately 780,000 practicing physicians in the U.S., 68% of them M.D.s, 25% international medical graduates (I.M.G.s), and 7% D.O.s. Although D.O. graduates make up the smallest percentage of practicing physicians, their numbers have been growing exponentially in recent years. It is estimated that by 2020, one in four medical school graduates in the United States will be a D.O.

Traditionally, a greater percentage of D.O. physicians (60%) practiced in primary care than M.D. physicians (35%). They treat 16% of patients in communities with fewer than 2,500 residents, which allopathic physicians often avoid.

D.O.s, M.D.s, and I.M.G.s all complete residencies after graduating from medical school, but these have traditionally involved separate programs. M.D.s and I.M.G.s may only attend M.D. residency programs, while D.O.s may attend either M.D. or D.O. programs.

Despite the seemingly large number of practitioners, America faces a looming physician shortage, particularly in primary care. The disjointed arrangement of residencies may be exacerbating the problem by limiting choices for some physicians.

In response, the organizations that accredit medical residencies, the Accreditation Council for Graduate Medical Education (ACGME), the American Osteopathic Association (AOA) and the American Association of Colleges of Osteopathic Medicine (AACOM), recently announced a plan to combine residency programs and implement a single, uniform accreditation process for D.O.s, M.D.s, and I.M.G.s.

This streamlining of residency programs could – in the long run – reduce costs significantly by eliminating duplicate efforts. Additionally, it could result in one set of uniform regulations for all physicians, rather than separate regulations for M.D.s and D.O.s.

However, some potential benefits of the streamlining are uncertain. For example, while joint accreditation would allow M.D.s and I.M.G.s to enter D.O. residency programs, it is unclear whether they would actually choose to do so – or whether program directors would accept them.

Additionally, it is possible that allowing M.D.s to attend D.O. residency programs could actually reduce the number of primary care physicians. M.D.s who do not get into more competitive specialty residencies often pursue residencies in the less competitive primary care field. However, with the combined programs, those M.D.s may attempt to get into a D.O. specialty residency, instead.

Finally, it is unclear how joint accreditation would work given that D.O. board examinations contain an OMM component and M.D. examinations do not.

It is laudable that the AOA, ACGME, and AACOM are considering ways to reduce the physician shortage and streamline costs and regulations. But it is important that osteopathic medicine remain distinct as an alternative to conventional medicine. It has existed for over a century and served its patients well. This should not be the beginning of its end.