UTILITY OF DIRECT MEASUREMENT OF LOW-DENSITY-LIPOPROTEIN CHOLESTEROL IN DYSLIPIDEMIC PEDIATRIC-PATIENTS

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 m eans of the Friedewald formula, an indirect calculation that requires an overnight fast. A new method has been developed for the direct meas urement of LDL-C (DLDL-C) that does not require fasting. We evaluated the clinical utility of this method. Design: We determined LDL-C conce ntrations simultaneously by the DLDL-C method, Friedewald equation, an d P-quantification (reference procedure). Setting: Pediatric dyslipide mia clinic at Children's Hospital, Boston, Mass. Patients: Ninety-two fasting hyperlipidemic pediatric patients. Results: At the LDL-C conce ntration cutoffs commonly used for making therapeutic decisions, the D LDL-C method had a significant negative bias (P less than or equal to .05) and misclassified patients into incorrect treatment groups more o ften than the Friedewald method. The negative predictive value for the DLDL-C method was lower than that for the Friedewald method (P less t han or equal to .05), and the cost of determining LDL-C level with the new method was 3 times greater. Conclusions: The misclassification po tential for LDL-C, and the assay costs, were greater for the DLDL-C me thod than for the Friedewald calculation. Despite the apparent advanta ges of the DLDL-C method, we conclude that for hyperlipidemic children the utility of this new method is not advantageous over the conventio nal Friedewald method. In some conditions, such as in diabetes or mark ed hypertriglyceridemia, the DLDL-C method may be useful.