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Editor's Correspondence
January 23, 2006

Why the Plasma TG/HDL-C Concentration Ratio Does Not Predict Insulin Resistance in African Americans

Arch Intern Med. 2006;166(2):249. doi:10.1001/archinte.166.2.249-a

We were somewhat surprised that Sumner et al1 evaluated the ability of plasma triglyceride (TG) concentration and/or the plasma TG/high-density lipoprotein cholesterol (HDL-C) concentration ratio to identify insulin resistance in 98 overweight and obese African Americans. We originally validated this diagnostic approach in 258 overweight and obese individuals, 87% of whom were white.2 In this ethnic group, insulin resistance is strongly correlated with both TG and HDL-C concentrations3—a prerequisite for their utility as markers of insulin resistance. As emphasized by Sumner and associates in this1 and a companion4 article, African Americans tend to be more insulin resistant compared with whites but have lower plasma TG concentrations. Thus, if insulin resistance and plasma TG concentration are not closely correlated, it would seem unlikely that plasma TG concentration or TG/HDL-C ratio would be useful in identifying insulin-resistant individuals. Because Sumner et al4 have shown that insulin resistance accounts for no more than 16% of the variability in plasma TG concentrations in African Americans, the finding1 that neither plasma TG concentration nor the TG/HDL-C ratio was a useful predictor of insulin resistance in this ethnic group was to be anticipated. To further emphasize that point, plasma TG concentration was only 87 mg/dL (0.98 mmol/L) in the most insulin-resistant third of the African American population1 compared with 168 mg/dL (1.90 mmol/L) in the most insulin-resistant third of the overweight and obese white individuals we studied.2

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