title: Comparison of LDL-cholesterol direct measurement with the estimate using the Friedewald formula in a sample of 10,664 patients.
abstract: OBJECTIVE
  To compare direct measurement of LDL-cholesterol (LDL-C) determined by a homogeneous method with LDL-cholesterol estimation determined by the Friedewald formula in a large heterogeneous population.
  
  
  METHODS
  The measurements of total cholesterol (TC) and triglycerides (TG) were performed using traditional enzymatic methods. The measurements of HDL-C and LDL-C were performed using direct methods with no precipitation, and the estimation of the LDL-C fraction was calculated using the Friedewald formula.
  
  
  RESULTS
  On linear regression analysis, the 2 methods had extremely significant correlation coefficients (P < 0.001). However, the Friedewald formula had a positive bias in regard to the direct method, more pronounced with TC levels > 201 mg/dL. This positive bias also occurred in regard to TG levels < or =150 mg/dL. No bias was observed between the methods for TG levels ranging from 151 to 200 mg/dL and from 201 to 300 mg/dL. On the other hand, for TG levels ranging from 301 to 400 mg/dL, this bias of the Friedewald formula became negative.
  
  
  CONCLUSIONS
  The Friedewald formula did not have a homogeneous performance for estimating LDL-C levels in samples with different TG levels as compared with that of the direct method, what could launch doubts on patients classification on the risk of developing coronary artery disease.
authors.affiliation: Departamento de Ciências Farmacêuticas, FURB, Laboratório Santa Isabel de Análises Clínicas, Blumenau, SC, Brazil. cmcordova@furb.br
authors.forename: Caio Maurício Mendes de
authors.initials: CM
authors.lastname: Cordova
authors.forename: Carlos Rudi
authors.initials: CR
authors.lastname: Schneider
authors.forename: Iara Deise
authors.initials: ID
authors.lastname: Juttel
authors.forename: Maurício Mendes de
authors.initials: MM
authors.lastname: Cordova
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002784:Cholesterol / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D014280:Triglycerides / Q000097:blood
chemical_list: D008078:Cholesterol, LDL; D014280:Triglycerides; D002784:Cholesterol