Background: The "lipid criteria" consist of a triglyceride (TG) level of 130 mg/dL (1.47 mmol/L) or greater and a ratio of TG to high-density lipoprotein cholesterol (HDL-C) of 3 or greater. In Caucasians, the lipid criteria predict insulin resistance in individuals with a body mass index (BMI) of 25 kg/m(2) or greater. Our goal was to determine whether TG levels or TG-HDL-C ratio predicted insulin resistance in African Americans with a BMI of 25 kg/m(2) or more.
Methods: Of 125 African Americans, the 98 with a BMI of 25 kg/m(2) or more participated. All subjects had frequently sampled intravenous glucose tolerance tests with insulin resistance determined by the insulin sensitivity index. Subjects were divided into the following tertiles by insulin sensitivity: 12.8 to 4.3, 4.2 to 2.3, and 2.2 to 0.2 mU/L per minute. Insulin resistance was defined as being in the third tertile. Across tertiles, the distribution of variables was compared by 1-way analysis of variance. Areas under the receiver operating characteristic curve were determined to identify variables that predicted insulin resistance.
Results: Fasting insulin level, BMI, and waist circumference increased across tertiles (all P<.01), but TG levels and TG-HDL-C ratio did not (all P>/=.3). The mean +/- SE areas under the curves for fasting insulin, BMI, and waist circumference were 0.85 +/- 0.04, 0.72 +/- 0.05, and 0.71 +/- 0.05, respectively. For TG level and TG-HDL-C ratio, the areas under the curves were 0.55 +/- 0.06 and 0.56 +/- 0.06, respectively, meaning that the true-positive rate was nearly equal to the false-positive rate. Therefore, they could not be used as markers of insulin resistance. Furthermore, 17 subjects met the lipid criteria but only 7 were in the insulin-resistant tertile, making the sensitivity of these criteria to identify insulin resistance only 17%.
Conclusion: In African Americans, TG levels and TG-HDL-C ratio are not reliable markers of insulin resistance.