Austrian researchers comparing the ability of two definitions of
metabolic syndrome to accurately predict the risk of developing
diabetes believe that the older National Cholesterol Education
Program Adult Treatment Panel (NCEP ATP) III definition is better
than the newer International Diabetes Federation (IDF) definition,
particularly in women.

Dr Bernhard Ludvik (Medical University of Vienna, Austria), who
presented the results of the analysis during the European Association
for the Study of Diabetes 2008 Meeting, told heartwire "I think it
was a bit premature to launch a new diagnosis for metabolic syndrome.
If you want to assess the risk of developing type 2 diabetes, it's
best to stick with the NCEP ATP III criteria."

IDF and NCEP ATP III Definitions

The IDF definition of metabolic syndrome requires someone to have
central obesity, defined by waist circumference, plus any two of the
following four factors: increased triglycerides or treatment thereof;
reduced HDL cholesterol or treatment thereof; increased blood
pressure or treatment thereof; or raised fasting plasma glucose or
previously diagnosed diabetes.

The NCEP ATP III definition of metabolic syndrome is slightly looser,
requiring someone to have three or more of the following: raised
fasting plasma glucose, elevated blood pressure, elevated
triglycerides, reduced HDL, and abdominal obesity, defined by waist
circumference.

Ludvik and colleagues collected parameters relevant to the diagnosis
of metabolic syndrome in 13 852 nondiabetic subjects (mean age 45)
and then followed them for an average of six years. Using the IDF
definition of metabolic syndrome, 13.3% of the cohort had metabolic
syndrome at baseline, whereas the overall number according to the
NCEP III definition was just 10.4%. Of note, concordance between the
two definitions was "modest," Ludvik said, expressed by a kappa value
of 0.63.

When metabolic-syndrome diagnosis was correlated with subsequent
development of diabetes over the follow-up period, both definitions
were found to be associated with an increased relative risk of
developing type 2 diabetes. In men, the relative risk for both
definitions was similar and not statistically different; however, in
women, the NCEP III definition was associated with a higher relative
risk of developing diabetes.

Ludvik et al concluded that while the prevalence of metabolic
syndrome in nondiabetic subjects was higher when the IDF definition
was used, the NCEP criteria, at least in women, "allow a better
assessment of the risk for type 2 diabetes," Ludvik said.

To heartwire, Ludvik hypothesized that because the NCEP criteria are
more broadly focused on specific cardiovascular risk factors, they
may have performed better in this particular group, which he said had
a higher prevalence of risk factors such as hypertension and
hyperlipidemia--the women in particular. But Ludvik also suggested
that the rapid adoption of the IDF criteria was "driven by external
factors," particularly pressure from industry to give particular
emphasis to waist circumference. Before this definition is used more
widely, Ludvik believes it should be better validated not only for
the prediction of type 2 diabetes, but also subsequent cardiovascular
disease.

In his own practice, he says he never uses the IDF criteria. Asked
whether he discusses the differences between the two definitions with
his patients, Ludvik pointed out: "Patients don't care about
metabolic syndrome, as long as they don't have diabetes."