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/m2 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/m2 or more.
Of 125 African Americans, the 98 with a BMI of 25 kg/m2 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.
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%.
In African Americans, TG levels and TG–HDL-C ratio are not reliable markers of insulin resistance.