Utility of direct measurement of low-density lipoprotein cholesterol in dyslipidemic pediatric patients

Abstract

Background: Low-density lipoprotein cholesterol (LDL-C) levels are the primary basis for treatment guidelines established for hyperlipidemic children and adolescents. Levels of LDL-C are commonly monitored by means of the Friedewald formula, an indirect calculation that requires an overnight fast. A new method has been developed for the direct measurement of LDL-C (DLDL-C) that does not require fasting. We evaluated the clinical utility of this method. Design: We determined LDL-C concentrations simultaneously by the DLDL-C method, Friedewald equation, and β-quantification (reference procedure). Setting: Pediatric dyslipidemia clinic at Children's Hospital, Boston, Mass. Patients: Ninety-two fasting hyperlipidemic pediatric patients. Results: At the LDL-C concentration cutoffs commonly used for making therapeutic decisions, the DLDL-C method had a significant negative bias (P≤.05) and misclassified patients into incorrect treatment groups more often than the Friedewald method. The negative predictive value for the DLDL- C method was lower than that for the Friedewald method (P≤.05), and the cost of determining LDL-C level with the new method was 3 times greater. Conclusions: The misclassification potential for LDL-C, and the assay costs, were greater for the DLDL-C method than for the Friedewald calculation. Despite the apparent advantages of the DLDL-C method, we conclude that for hyperlipidemic children the utility of this new method is not advantageous over the conventional Friedewald method. In some conditions, such as in diabetes or marked hyper-triglyceridemia, the DLDL-C method may be useful.