title: Application of a modified precipitation method for the measurement of small dense LDL-cholesterol (sd-LDL-C) in a population in southern Brazil.
abstract: BACKGROUND
  In the study reported herein, we used the precipitation method employing heparin-Mg(2+), with slight modifications to avoid lipemia interference, to measure small dense-low density lipoprotein-cholesterol (sd-LDL-C) in Brazilian subjects with a high risk of developing cardiovascular diseases.
  
  
  METHODS
  Lipemic samples were diluted with various solvents prior to precipitation with heparin-Mg(2+). Validation assays were performed with ultracentrifugation (n=100) and the reproducibility of sd-LDL-C measured in diluted serum (n=50). The applicability of this modification was evaluated by measuring sd-LDL-C in 434 southern Brazilian normolipidemic, dyslipidemic and type 2 diabetes mellitus (T2DM) individuals.
  
  
  RESULTS
  Lipemic serum diluted with 100 mmol/L phosphate buffer pH 8.5 was effective for the quantification of sd-LDL-C, which was correlated with non-diluted serum (r=0.961; p<0.0001) and with ultracentrifugation (r=0.705; p<0.0001). Ultracentrifugation sd-LDL-C was 0.08 mmol/L (CI 95%: -0.42-0.58 mmol/L) higher than the precipitation method (p>0.05). Subjects with dyslipidemias and T2DM had, respectively, 2.3 and 2.6-fold higher sd-LDL-C concentrations than normolipidemic individuals (p<0.05). The incidence of normolipidemic subjects with a high concentration of sd-LDL-C was only 2.2%. The sd-LDL-C was found to be enhanced by 8.3% every 10 years and young normolipidemic men had 24% higher sd-LDL-C than young women (p<0.05). Lipid-lowering therapy reduced sd-LDL-C by 26% (p<0.001).
  
  
  CONCLUSIONS
  In this paper we described a simple and inexpensive approach to improving the measurement of sd-LDL-C in high-triglycerides serum. Furthermore, we showed that southern Brazil dyslipidemic and T2DM individuals have increased sd-LDL-C concentrations.
authors.affiliation: Post-Graduation Program in Pharmacy, Department of Clinical Analyses, Health Sciences Center, Federal University of Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: Luciana da S
authors.initials: Lda S
authors.lastname: Cavalcante
authors.forename: Edson L
authors.initials: EL
authors.lastname: da Silva
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil; D011232:Chemical Precipitation; D008078:Cholesterol, LDL / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood; D050171:Dyslipidemias / Q000097:blood; D005260:Female; D006493:Heparin / Q000737:chemistry; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood; D007477:Ions / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000737:chemistry; D014461:Ultracentrifugation; D055815:Young Adult
chemical_list: D008078:Cholesterol, LDL; D007477:Ions; D014280:Triglycerides; D006493:Heparin; D008274:Magnesium