BOSTON — When using triglycerides to identify insulin resistance, patient ethnicity must be taken into account.
An assessment of the relationship between insulin resistance and triglycerides in nearly 6,000 individuals representing four ethnic groups has shown that although a triglyceride level above 150 mg/dL is a reasonable predictor of insulin resistance in non-Hispanic white and Chinese individuals, it is a poor predictor in African Americans and Hispanic individuals, Dr. Preethi Srikanthan said at the Fifth Annual World Congress on the Insulin Resistance Syndrome.
Similarly, a triglyceride level lower than 150 mg/dL reasonably predicts the absence of insulin resistance in non-Hispanic whites and Chinese individuals. But the same is not seen in African Americans or Hispanic individuals.
Triglyceride levels are often used as a proxy measurement for identifying insulin resistance in the clinical setting, said Dr. Srikanthan of the University of California, Los Angeles. Elevated triglycerides—those over a threshold value of 150 mg/dL—are used as evidence of insulin resistance, and normal triglyceride levels are thought to indicate the absence of insulin resistance.
But because this assessment method does not take into consideration possible racial or ethnic differences in metabolic parameters, Dr. Srikanthan and colleagues sought to gauge its predictive accuracy across ethnic populations.
Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), a multicenter investigation into the characteristics of subclinical cardiovascular disease and risk factors that predict progression to clinically overt cardiovascular disease, the researchers evaluated the relationship between insulin resistance and triglyceride levels above the 150 mg/dL threshold in four ethnic groups. The study included 5,997 nondiabetic participants of which 1,594 were African American (mean age 62 years), 1,239 were Hispanic (mean age 61 years), 2,463 were non-Hispanic whites (mean age 62 years), and 701 were Chinese (mean age 62 years).
They calculated the homeostasis model assessment of insulin resistance (HOMA-IR) using participants' fasting insulin and glucose values. Participants with HOMA-IR values in the upper quartile (greater than 2.32) were classified as having insulin resistance. Triglyceride levels were compared on a log scale by ethnicity using one-way analysis of variance with multiple comparison correction, Dr. Srikanthan said.
Of the full study population, 23% of the African American group, 56% of the Hispanic group, 55% of the non-Hispanic white group, and 66% of the Chinese group were insulin resistant with triglyceride levels greater than 150 mg/dL.
By comparison, insulin resistance with triglyceride levels at or below 150 mg/dL was noted in 18% of the African American group, 19% of the Hispanic group, 6% of the non-Hispanic white group, and 7% of the Chinese group, said Dr. Srikanthan.
To measure the accuracy of triglycerides as predictors of insulin resistance, the researchers computed area under receiver operating characteristic (ROC) curves. In the African American and Hispanic groups, the areas under ROC curves of insulin resistance by triglyceride level were 0.62 and 0.64, respectively, suggesting triglyceride status relative to the 150-mg/dL threshold is a poor predictor of insulin resistance status. In contrast, the areas under ROC curves of insulin resistance by triglyceride levels in the non-Hispanic white and Chinese participants were 0.73 and 0.75, respectively, indicating fair predictive accuracy.
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