Public Release: 

Defining "Medical Necessity"

Public Health Reports

Encouraging informed patients to share in the decision-making process results in a different definition of what can be termed "medically necessary." In his commentary, Medical Necessity and the Debate over [Expletive Deleted] Care, John E. Wennberg, MD, MPH of Dartmouth Medical School, begins:

"Fill in the deleted expletive. South of the Canadian border, what springs to mind is "managed" care; north of the border, it is "private" care. While the underlying reason for the debate is the same"relentless growth in the proportion of the gross domestic product allocated to health care"the situations and solutions are quite different."

Wennberg argues "in both nations we have failed to confront the conundrum of what constitutes medical necessity and therefore our ability to identify when valuable care is being rationed. Traditionally, medical necessity is dictated by what the doctor prescribes, and most policy analysts and patients have been raised to assume that the basis for doctors' prescriptions is medical science and the physician's unerring judgment about what is best for the patient. Since, under this assumption, care is manifestly efficacious and of value to patients, care is perceived to be rationed when, for whatever reason, limits are imposed on available resources."

The only way to know what treatment eligible patients want is to ask them and to do so in a setting that empowers them to choose according to their own preferences. Research on practice variation provides strong, albeit circumstantial, evidence that patient choice is not now determining the rates of use of surgery. The smaller the geographic unit of analysis, the wider the variation: data from Ontario show that the rates for discretionary surgery vary much more among the 33 District Health Councils in that province than they vary between provinces. In 1994-1995, lens extractions for cataracts ranged from a low of 5.3 to a high of 25.7 per 1000 residents 50 years and older, almost a fivefold range of variation. Coronary artery bypass procedures per 1000 residents 20 years and older ranged from a low of 0.4 to a high of 1.5, more than a threefold difference, and transurethral prostatectomies ranged from 0.6 to 1.3 per 1000 residents 50 years and older, differing by a factor of more than two.

Research on shared decision-making--a strategy of clinical decision-making in which patients are fully informed about what is known and not known about the outcomes of care (based on evidence-based technology assessments) and invited to participate in the choice of treatment--provides evidence that demand for discretionary care changes when the patient is brought into the equation. Barry et al. report a 40% decline in utilization rates in two staff model health maintenance organizations (HMOs) once patients were offered shared decision-making. In a clinical trial in Toronto of shared decision-making about treatments for coronary artery disease, Detsky et al. found a 23% reduction in use of invasive treatment for coronary artery disease among patients randomized to shared decision making, compared to controls. It is noteworthy that these studies were each conducted among groups in which the rates of surgery have been low compared to most populations in North America. The implication is that under shared decision-making, the demand for care may be substantially less than the amount now prescribed by physicians or approved by managed care companies.

Quite apart from this consideration, however, the movement to shared decision-making offers the profession the opportunity to insure patients that the use of discretionary care is in the best interest of the individual patient. If the bonus is reduced pressure on the expansion of resources devoted to elective surgery, so much the better for the beleaguered North American delivery systems, whether private or public.

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NOTE: This memo to reporters is from the journal staff and is not an official release of the US Public Health Service; nor does it reflect USPHS policy.

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