The Triglyceride/High-Density Lipoprotein Cholesterol Ratio Fails to Predict Insulin Resistance in African-American Women: An Analysis of Jackson Heart Study

Background: Compared to whites, insulin-resistant African Americans have worse outcomes. Screening programs that could identify insulin resistance early enough for intervention to affect outcome often rely on triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) levels. Racial differences in TG and HDL-C may compromise the efficacy of these programs in African Americans. A recommendation currently exists to use the TG/HDL-C ratio >= 2.0 to predict insulin resistance in African Americans. The validity of this recommendation needs examination. Therefore, our aim was to determine the ability of TG/HDL-C ratio to predict insulin resistance in African Americans. Methods: In 1,903 African Americans [895 men, 1,008 women, age 55 +/- 12 years, mean +/- standard deviation (SD), range 35-80 years, body mass index (BMI) 31.0 +/- 6.4 kg/m(2), range 18.5-55 kg/m2] participating in the Jackson Heart Study, a population-based study of African Americans, Jackson, Mississippi tricounty region, insulin resistance was defined by the upper quartile (>= 4.43) of homeostasis model assessment of insulin resistance (HOMA-IR). An area under the receiver operating characteristic curve (AUC-ROC) of >0.70 was required for prediction of insulin resistance by TG/HDL-C. The optimal test cutoff was determined by the Youden index. Results: HOMA-IR was similar in men and women (3.40 +/- 2.03 vs. 3.80 +/- 2.46, P = 0.60). Women had lower TG (94 +/- 49 vs. 109 +/- 65 mg/dL P < 0.001) and TG/HDL-C (1.9 +/- 1.4 vs. 2.7 +/- 2.1, P < 0.001). For men, AUC-ROC for prediction of insulin resistance by TG/HDL-C was: 0.77 +/- 0.01, mean +/- standard error (SE), with an optimal cutoff of >= 2.5. For women, the AUC-ROC was 0.66 +/- 0.01, rendering an optimal cutoff indefinable. When women were divided in two groups according to age, 35-50 years and 51-80 years, the results did not change. Conclusions: In African-American men, the recommended TG/HDL-C threshold of 2.0 should be adjusted upward to 2.5. In African-American women, TG/HDL-C cannot identify insulin resistance. The Jackson Heart Study can help determine the efficacy of screening programs in African Americans.