Comparison of Direct and Indirect Measurement of LDL-C in HIV-Infected Individuals: ACTG 5087

Abstract

Background: Hypertriglyceridemia is common in HIV-infected individuals on antiretroviral therapy. Triglyceride (TG) levels >400 mg/dL interfere with the accurate determination of low-density lipoproteins (LDL-C) by the Friedewald equation, making it difficult to assess coronary heart disease risk. Objective: The objective of this study is to compare the agreement of the direct LDL-C assay and the Friedewald equation with a reference ultracentrifugation method in the estimation of LDL-C concentrations. Method: Samples from ACTG 5087 were assayed by ultracentrifugation and a direct enzymatic assay and calculated using the Friedewald equation. Results: In subjects with TG <400 mg/dL (n = 271), 90% of the direct LDL-C values and Friedewald calculations were within 30 mg/dL and 32 mg/dL of the ultracentrifugation values, respectively. With TG ⩾400 mg/dL (n = 186), 90% of the direct assay and Friedewald observations were within 68 mg/dL and 120 mg/dL of the ultracentrifugation results, respectively. Only 27% of the LDL-C values were within 15 mg/dL of the ultracentrifugation LDL-C results for direct assay and 16.3% for the Friedewald equation. Conclusion: The direct LDL-C assay and the calculated LDL-C values did not display adequate agreement with the reference ultracentrifugation method. In subjects with TG >400 mg/dL, the direct assay overestimates the actual LDL-C whereas the Friedewald calculation underestimates the actual LDL. Clinical usage of these methods may lead to misclassification of the severity of dyslipidemia, resulting in improper management.

Keywords:

• low-density lipoproteins
• hypertriglyceridemia
• Friedewald equation
• coronary heart disease