title: Underestimation of Low Density Lipoprotein-Cholesterol With the Friedewald Equation Versus a Direct Homogenous Low Density Lipoprotein-Cholesterol Assay.
abstract: BACKGROUND
  Low-density lipoprotein cholesterol (LDL-C) concentrations are the primary therapeutic target in patients with atherosclerotic cardiovascular disease (ASCVD). However, at low LDL-C concentrations, there is a significant underestimation using the Friedewald equation compared with ultracentrifugation.
  
  
  METHODS
  In this pilot study, we compared LDL-C concentrations obtained using the Friedewald equation (LDL-F) vs those concentrations from a direct LDL-C (LDL-D) assay in 152 consecutive specimens from patients with triglyceride levels between 200-399 mg/dL and LDL-F <100 mg/dL. Also, we compared LDL-F and LDL-D results to the novel formula (LDL-N).
  
  
  RESULTS
  The LDL-F value was significantly lower than that of LDL-D when LDL concentrations were 70-99 mg/dL (P <.001, 14% negative bias), and this decrease was accentuated in specimens with LDL <70 mg/dL, (P <.001, 27% negative bias). When compared with the LDL-N value, LDL-F and LDL-D values showed a 17% and 2% negative bias for specimens with LDL-C values of 70-99 mg/dL and 36% and 1% negative bias, respectively, at LDL-C <70 mg/dL (P <.001 for comparisons of LDL-F and LDL-N values).
  
  
  CONCLUSIONS
  To provide accurate LDL-C levels in patients at high risk for ASCVD, if beta quantification by ultracentrifugation is unavailable and if LDL-C is <100 mg/dL and triglycerides are 200-399 mg/dL, laboratories should revert to direct LDL-C measurements or use the novel formula. Although LDL-N is more cost-effective, LDL-D can be run on most platforms, does not require a specimen from a fasting individual, is standardized, and has the advantage of being validated in large trials such as the Heart Protection Study.
authors.affiliation: Medical Services, Veterans Affairs Medical Center, Mather, CA.|Department of Pathology and Metabolism, California Northstate University, College of Medicine, Elk Grove, CA.
authors.forename: Ishwarlal
authors.initials: I
authors.lastname: Jialal
authors.affiliation: Medical Services, Veterans Affairs Medical Center, Mather, CA.
authors.forename: Michael
authors.initials: M
authors.lastname: Inn
authors.affiliation: Medical Services, Veterans Affairs Medical Center, Mather, CA.
authors.forename: David
authors.initials: D
authors.lastname: Siegel
authors.affiliation: Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX.
authors.forename: Sridevi
authors.initials: S
authors.lastname: Devaraj
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D008078:Cholesterol, LDL / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D015203:Reproducibility of Results
chemical_list: D008078:Cholesterol, LDL
keywords: Friedewald equation; LDL; direct LDL-cholesterol; heart disease; homogenous assays; triglycerides