title: Direct measurement of LDL-C in children: performance of two surfactant-based methods in a general pediatric population.
abstract: OBJECTIVE
  Several pediatric advisory groups have recommended selective screening for dyslipidemia in children. Low-density lipoprotein cholesterol (LDL-C) is measured clinically with the Friedewald calculation in fasting samples. Nonfasting measurement of LDL-C would be clinically useful in children.
  
  
  METHODS
  In the present study, we examine the performance of two surfactant-based direct LDL-C assays in paired samples, fasting and nonfasting, from 100 children.
  
  
  RESULTS
  LDL-C in the fasting state was significantly lower with the Friedewald estimation: 2.43 +/- 0. 61 mmol/L, N-geneous (Genzyme Corp.) direct LDL-C: 2.30 +/- 0.59 mmol/L, and Roche (Roche Diagnostics) direct LDL-C: 2.32 +/- 0.57 mmol/L than with ultracentrifugation-dextran-sulfate-Mg(2+) precipitation (UC-DS): 2.47 +/- 0.64 mmol/L. Moreover, there was increased negative bias using nonfasting samples with N-geneous: 2. 25 +/- 0.56 mmol/L and Roche: 2.26 +/- 0.56 mmol/L compared with fasting UC-DS. Correlation with US-DS was highest for Friedewald (r = 0.974) and fasting N-geneous (r = 0.973), and lowest with nonfasting N-geneous (r = 0.849) and Roche in fasting (r = 0.891) and nonfasting samples (r = 0.747). The sensitivity at LDL-C concentration of 2.85 mmol/L for the two direct methods when either fasting or nonfasting samples were used, was lower than that obtained with Friedewald.
  
  
  CONCLUSIONS
  Overall, these direct LDL-C assays demonstrated limited utility in screening children but may be useful in the management of lipid disorders.
authors.affiliation: From the Department of Pathology and Laboratory Medicine, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: H H
authors.initials: HH
authors.lastname: Yu
authors.forename: R
authors.initials: R
authors.lastname: Markowitz
authors.forename: S D
authors.initials: SD
authors.lastname: De Ferranti
authors.forename: E J
authors.initials: EJ
authors.lastname: Neufeld
authors.forename: G
authors.initials: G
authors.lastname: Farrow
authors.forename: H H
authors.initials: HH
authors.lastname: Bernstein
authors.forename: N
authors.initials: N
authors.lastname: Rifai
mesh_terms: D001322:Autoanalysis / Q000379:methods; D001900:Boston; D002648:Child; D002662:Child Health Services; D002675:Child, Preschool; D002784:Cholesterol / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D004435:Eating; D005215:Fasting; D005260:Female; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood / Q000175:diagnosis*; D008297:Male; D011933:Reagent Kits, Diagnostic; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results; D013501:Surface-Active Agents; D014280:Triglycerides / Q000097:blood
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D011933:Reagent Kits, Diagnostic; D013501:Surface-Active Agents; D014280:Triglycerides; D002784:Cholesterol