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Unwarranted variation

Unwarranted Variation, first termed by Dr. John Wennberg in his decades of research, can be defined as differences in healthcare service delivery that cannot be explained by illness, medical need, or dictates of evidence-based medicine, and can be classified into one of three categories:

  • Effective care and patient safety, which includes services of proven clinical effectiveness, such as using lipid lowering agents in patients with coronary artery disease.
  • Preference-sensitive care, treatment for conditions that have significant trade-offs in terms of risks and benefits for the patient. But the choice of care is, or should be, driven by the patient’s own preferences.
  • Supply-sensitive care, care which is strongly correlated with healthcare system resource capacity and is generally provided in the absence of medical evidence and clinical theory.


Working in 1967 in the Regional Medical Program created with a $350,000 grant from President Lyndon B. Johnson, Dr. Wennberg was analyzing Medicare data to determine how well hospitals and doctors were serving their communities.

"Our results were fascinating, because they ran completely counter to what conventional wisdom said they would be," he told me during the interview in his cozy New Hampshire home. "Everyone expected that we would clearly see underservice in the rural hospital service areas remote from academic medical centers. But when we looked at the data, we found tremendous variation in every aspect of healthcare delivery, even among communities served by academic medical centers. We found the same thing when we compared healthcare in the Boston and New Haven communities served by some of the finest academic medical centers in the world. The basic premise-that medicine was driven by science and by physicians capable of making clinical decisions based on well-established fact and theory-was simply incompatible with the data we saw. It was immediately apparent that suppliers were more important in driving demand than had been previously realized.

As described by Health Dialog, the company established to educate the healthcare industry on Unwarranted Variation:

If you live in northern Idaho, and you develop back pain, chances are good that you’ll undergo surgery to treat your pain. Move to the southern tip of Texas, however, and the chances that you’ll undergo that same surgery will drop by a factor of 6. The surgery is no more effective in Idaho than it is in Texas. It’s just that doctors in the northwest are more likely than those in southern Texas to recommend surgery. This phenomenon, in which doctors practice medicine differently depending on where they’re from, is called practice pattern variation. And it isn’t limited to treating back pain, or even surgical decisions. There is also variation in treatment for chronic conditions, such as use of beta blockers for individuals with Congestive Heart Failure (CHF) or lipid testing for those with diabetes.

Dr. Wennberg and his colleagues at the Dartmouth Center for Evaluative Clinical Sciences have documented these wide variations in how healthcare is practiced around the country. They have also asserted that most of this variation is, in fact, unwarranted. Health Dialog was built to directly address unwarranted variation in healthcare: the overuse, underuse and misuse of medical care. Wennberg and his colleagues further concluded that if unwarranted variation in the healthcare system could be reduced, the quality of care would go up and healthcare costs would go down. Studies have shown that if unwarranted variation could be reduced in the Medicare population, quality of care would rise dramatically and costs could be lowered by as much as 30%.

Unwarranted Variation Today

Unwarranted variation in medical practice, as noted by Martin Sipkoff in 9 Ways To Reduce Unwarranted Variation, is costly — and deadly. Analysis of Medicare data reveals that per-capita spending per enrollee in Miami is almost 2.5× as great as in Minneapolis, even after adjusting data for age, sex, and race. Worse, 57,000 lives are lost annually because physicians aren't using evidence-based medicine to guide their care, according to a recent report from the National Committee for Quality Assurance.

"We're literally dying, waiting for the practice of medicine to catch up with medical knowledge," says Margaret O'Kane, president of NCQA. The report, "The State of Health Care Quality 2003," says these deaths "should not be confused with those attributable to medical errors or lack of access to health care. This report shows that a thousand Americans die each week because the care they get is not consistent with the care that medical science tells us they should get.

"Practice variation is one of the greatest problems we face in controlling costs, but we believe that it is something we can do something about." Dwayne Davis, MD, medical director of Geisinger Health Care
A presentation on Unwarranted Variation from Dr. John Wennberg can be seen on the Dartmouth website
Unwarranted variation in the United States

  • Studies show that individuals with diabetes should have blood lipids monitored regularly, yet patients in Chicago are 50% less likely to receive these tests than patients in Fort Lauderdale.
  • A patient with heart disease in Bloomington, Indiana, is three times more likely to have bypass surgery than a similar patient in Albuquerque.
  • In Miami, where medical services are abundant, Medicare pays more than twice as much per person per year as it does in Minneapolis, with no discernible difference in overall health or life expectancy.

Articles on Unwarranted Variation

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