Critics question usefulness of metabolic syndrome diagnosis

Some say the syndrome is no more than the sum of its parts, while others cite its value as a predictor for diabetes and heart disease.

By Susan J. Landers — Posted Sept. 19, 2005

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Washington -- Has metabolic syndrome become a misleading diagnosis or a helpful tool?

A debate is under way over the benefit to patients of clustering a number of risk factors for diabetes and heart disease into this specifically named constellation of symptoms.

An opening volley in this dispute included charges that the syndrome is poorly defined, inconsistently used and in need of further research. It was fired by the American Diabetes Assn. in a joint paper with its European counterpart, the European Assn. for the Study of Diabetes, and published in the September issues of Diabetes Care and Diabetologia.

Now caught in the crossfire are as many as 47 million overweight Americans whose blood pressure, triglycerides and fasting glucose levels are high and whose good cholesterol levels are not sufficient to provide necessary protection against rising rates of diabetes and cardiovascular disease.

The enormity of the public health problem these diseases pose, combined with the syndrome's apparent predictive value for risk, should be reason enough to ensure metabolic syndrome a place in the physician's tool box, say its proponents.

But critics aren't so sure. They stress the need for primary care physicians to pay more heed to the syndrome's individual components rather than be distracted by a grouping of symptoms known by many monikers -- including the more mysterious, syndrome X -- and not supported by solid research.

"There are lots of people saying to patients, 'You've got the metabolic syndrome,' " said Richard Kahn, PhD, chief scientific and medical officer of the American Diabetes Assn. Dr. Kahn is a lead author of the new paper. "But what does that mean?"

Until more research is conducted, it means very little, he added. "You could be putting a label on someone unnecessarily."

Although the factors that make up metabolic syndrome are well-known cardiovascular risks, combining them does not add up to a more significant risk. "If we could find some criteria, the existing ones or some others, where you could add up one plus one plus one and get four and not three, then maybe you'd have something," Dr. Kahn said.

In addition, he faulted the syndrome's variety of definitions that make it even harder to pin down. The National Cholesterol Education Program, the World Health Organization and the International Diabetes Federation have published different descriptions, although the risk factors are essentially the same.

On the other hand

Meanwhile the American Heart Assn. remains supportive of metabolic syndrome, calling it a useful tool to help doctors reduce diabetes and cardiovascular risk among patients.

"Studies have shown that individuals with the metabolic syndrome, defined by NCEP criteria, have double the risk for cardiovascular disease, and their risk for type 2 diabetes is increased about five times," according to an AHA statement.

The syndrome was developed several years ago and was recently refined to draw the attention of physicians to their patients at risk for heart disease beyond determining who had high LDL cholesterol levels, and it has done that, said AHA President Robert Eckel, MD.

"Metabolic syndrome is well-established worldwide as a diagnostic entity," Dr. Eckel said. He acknowledged that the ADA and the EASD raise legitimate questions about differences in definition and the syndrome's path of physiology. "[But] we believe this is something worth preserving."

The syndrome focuses attention on lifestyle changes as an important means for lowering risk, Dr. Eckel said. "Interestingly enough, addressing the individual risk factors has proven not to be all that predictive of benefit. Lowering blood pressure is the component we have the most evidence for as being effective at reducing heart disease and stroke risk."

Statistics reflecting soaring rates of obesity and diabetes demonstrate that physicians aren't doing a terrific job at preventing these well-recognized health threats, said Christie Ballantyne, MD, director of the Center for Cardiovascular Disease Prevention at Methodist DeBakey Heart Center in Houston.

Dr. Ballantyne uses the metabolic syndrome as a teaching tool for patients whose triglycerides are high, HDL cholesterol is low, glucose is borderline and blood pressure is a little elevated, and who have gained some weight.

"It helps take something very complicated and make some sense out of it. I don't see what's wrong with it," Dr. Ballantyne said.

Michael Fleming, MD, a family physician in Shreveport, La., calls the debate over the syndrome an academic exercise. "I think [metabolic syndrome] is useful as a concept," he said. "We can argue over whether there is such a thing and what the definition is -- it would be helpful to know -- but that's not going to change the way I deal with patients, because that group of patients [with the syndrome's characteristic components] is at high risk."

Meanwhile, work is under way to examine the syndrome.

The Endocrine Society already has an international task force working on guidelines for treating it, and the American Assn. of Clinical Endocrinologists, in response to the diabetes groups' paper, is re-evaluating the concept, which it calls insulin-resistance syndrome. The AACE expects to report its findings by Sept. 30.

"When organizations of the stature of the ADA and the EASD suggest it's time for a critical appraisal of metabolic syndrome, it's appropriate that organizations such as AACE, who have looked at this topic in the past and have created a position statement, need to respond by doing exactly that," said AACE President Bill Law, MD.

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What they look for

The Third Report of the National Cholesterol Education Program includes one definition of metabolic syndrome that is referred to commonly. There are others. The clinical identifiers developed by the NCEP in 2001 include:

  • Abdominal obesity, which for men was defined as a waist circumference of more than 40 inches and for women a circumference of more than 35 inches
  • Triglycerides greater than or equal to 150 mg/dL
  • HDL cholesterol levels for men of less than 40 mg/dL; for women less than 50 mg/dL
  • Blood pressure greater than or equal to 130/85 mmHg
  • Fasting glucose of greater than or equal to 110 mg/dL

Source: National Cholesterol Education Program

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