New Joint Statement Streamlines Definition of Metabolic Syndrome

From Heartwire CME

October 12, 2009 — A new joint statement from a number of professional organizations has identified specific criteria for the clinical diagnosis of the metabolic syndrome, tightening up the definition, which previously differed from one organization to the next [1].
The statement, published online October 5, 2009, in Circulation, includes the participation of the International Diabetes Federation (IDF), the National Heart, Lung, and Blood Institute (NHLBI), the World Heart Federation, the International Atherosclerosis Society, and the American Heart Association (AHA) and is an attempt to eliminate some of the confusion regarding how to identify patients with the syndrome.
"This paper represents an attempt to make the definition global," Dr Robert Eckel (University of Colorado, Denver), one of the authors of the new report, told heartwire . "The IDF definition and the [National Cholesterol Education Program Adult Treatment Panel] ATP III definition have been the two that have been utilized most frequently, and now the different organizations--the IDF, the International Atherosclerosis Society, the NHLBI, and the AHA--have all signed on to a single definition. I think that's a step forward in terms of not continuing to confuse people who are working in this field."
Specifically, the new metabolic-syndrome definition streamlines previous differences related to abdominal obesity as defined by measurements in waist circumference. Substantial disparities existed between the previous IDF and the ATP III definitions of what constituted an excessively large waist circumference, by as much as 8 cm between the two groups, but these have been amended. Now, the criteria for elevated waist circumference are based on population- and country-specific definitions, which, although streamlined, do leave some work to be done, said Eckel.
"The problem that still exists is that regional differences around the world may be substantial in terms of what waist circumference confers additional risk for heart disease and diabetes," he said. "The new definition relies on different geographic regions, or different countries, to drill down into their own databases in terms of relating waist circumference to risk." Eckel noted that the IDF previously considered elevations in waist circumference mandatory when defining metabolic syndrome, although the ATP III did not. Now, waist circumference is just one of five criteria that physicians can use when diagnosing the metabolic syndrome. Patients with three of the five criteria--including elevated waist circumference, elevated triglycerides, reduced high-density lipoprotein (HDL)-cholesterol levels, elevated blood pressure, and elevated fasting-glucose levels--are considered to have the syndrome.

Criteria for Clinical Diagnosis of the Metabolic Syndrome

Measure	Categorical cut points
Elevated waist circumference	Population- and country-specific definitions
Elevated triglycerides (drug treatment for elevated triglycerides is an alternate indicator)	>150 mg/dL
Reduced HDL cholesterol (drug treatment for reduced HDL cholesterol is an alternate indicator)	<40 mg/dL for males and <50 mg/dL for females
Elevated blood pressure (drug treatment for elevated blood pressure is an alternate indicator)	Systolic >130 mm Hg and/or diastolic >85 mm Hg
Elevated fasting glucose (drug treatment for elevated glucose is an alternate indicator)	>100 mg/dL

Notably absent from the joint statement is the American Diabetes Association. As reported by heartwire , there are unresolved scientific issues between the ADA and other associations, including the AHA, regarding the metabolic syndrome. Specifically, the ADA, as well as the European Association for the Study of Diabetes (EASD), objected to the manner in which the metabolic syndrome was characterized as a risk factor for heart disease or diabetes, arguing that there was no need to diagnose a patient with the syndrome because emphasis should be placed on aggressively treating the individual risk factors. In 2005, the ADA and EASD issued their own joint statement calling for a critical appraisal of the metabolic syndrome, its designation as a syndrome, and its clinical utility.
To heartwire , Eckel said the IDF, AHA, NHLBI, and others began working on the new metabolic syndrome definition in 2008 and that they simply went ahead without ADA participation. He stressed the metabolic syndrome is not a disease but simply a clustering of risk factors. The original intention of identifying the syndrome was simply to draw clinicians' and the public's attention to the importance of a high-quality lifestyle, and the metabolic syndrome is never meant to be used as a predictor of heart disease or diabetes risk.

Clinical Context

The metabolic syndrome has received significant attention because of its role in disease. In general, patients with this syndrome exhibit a proinflammatory state, and, in addition to high serum levels of triglycerides and low levels of high-density lipoprotein cholesterol, they tend to have high levels of apolipoprotein B and elevations in small low-density lipoprotein particles. All of these factors contribute to doubling the risk for incident cardiovascular disease within 5 to 10 years as well as a 5-fold increase in the risk for incident type 2 diabetes.
Despite the importance of the metabolic syndrome as a risk marker, there remains disagreement regarding the best way to define it. The current scientific statement attempts to clarify the definition of metabolic syndrome and identifies possible future refinements to this definition.

Study Highlights

• The primary factors used to define the metabolic syndrome have been atherogenic dyslipidemia, elevated blood pressure, and elevated blood glucose levels.
• Whereas some criteria for metabolic syndrome excluded patients with existing type 2 diabetes, current recommendations do not.
• The most significant controversy regarding the definition of the metabolic syndrome has been the inclusion of abdominal obesity. It has been required in some recommendations to diagnose the metabolic syndrome, whereas it has served as a nonintegral variable in the diagnosis in other algorithms.
• Moreover, the definition of abdominal obesity is challenging. Predictive values for various levels of abdominal obesity for cardiovascular disease and diabetes may differ. Different health systems may define abdominal obesity based on more strict or loose criteria to satisfy pragmatic public health or economic concerns.
• Most important, the waist circumference threshold for abdominal obesity varies according to sex and ethnic group. For example, the World Health Organization cutoff values for abdominal obesity for Caucasians are 94 cm or more and 80 cm or more for men and women, respectively. Their respective cutoff values for Asian men and women are 90 cm and 80 cm, and the Japanese Obesity Society defines its respective cutoff values at 85 cm and 90 cm.
• The population-specific method of defining abdominal obesity is also limited by a lack of information from large regions, including the Middle East and Africa.
• At the same time, the use of common diagnostic thresholds across international borders and types of patients will make the diagnosis of metabolic syndrome easier to understand and treat.
• Using recommendations from the different organizations, the authors of the current scientific statement therefore recommend 5 specific criteria and categorical cutoff points to diagnose metabolic syndrome. Patients with at least 3 of these 5 criteria may be considered to have the diagnosis. The criteria are as follows:
  
  • Elevated triglyceride levels or drug treatment of these elevated levels (≥ 150 mg/dL [≥ 1.7 mmol/L])
  • Reduced HDL cholesterol levels or drug treatment of these reduced levels (< 40 mg/dL [1.0 mmol/L] in men; < 50 mg/dL [1.3 mmol/L] in women)
  • Elevated blood pressure or treatment of hypertension (systolic 130 mm Hg and/or diastolic ≥ 85 mm Hg)
  • Elevated fasting glucose levels or treatment with antihyperglycemic medications (≥ 100 mg/dL)
  • Elevated waist circumference (population- and country-specific definitions)
  
  
• New data should emerge, which may help to determine a standard definition for elevated waist circumference, and additional meetings between lead organizations will focus on the development of a single set of diagnostic criteria for metabolic syndrome.

Clinical Implications

• The metabolic syndrome is associated with high levels of apolipoprotein B and increases in small low-density lipoprotein particles as well as a 2-fold increase in the risk for incident cardiovascular disease and a 5-fold increase in the risk for incident type 2 diabetes.
• The current international guidelines set cutoff points for 4 of the 5 criteria that contribute to the diagnosis of metabolic syndrome, but the variability of waist circumference based on sex and race makes a uniform definition for abdominal obesity difficult.