title: Variability of serial lipoprotein-associated phospholipase A2 measurements in post myocardial infarction patients: results from the AIRGENE Study Center Augsburg.
abstract: BACKGROUND
  Of the numerous emerging biomarkers for coronary heart disease (CHD), lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), an enzyme involved in lipid metabolism and inflammatory pathways, seems to be a promising candidate. Implementation of Lp-PLA(2) measurement into clinical practice, however, requires data on the reliability of such measurements.
  
  
  METHODS
  We measured Lp-PLA(2) concentrations by ELISA in blood samples drawn from 200 post-myocardial infarction patients (39-76 years) at 6 monthly intervals between May 2003 and February 2004, for a total of 1143 samples. We estimated analytical, within-individual, and between-individual variation, the critical difference, and the intraclass correlation coefficient of reliability (ICC) to assess the reliability of serial Lp-PLA(2) measurements.
  
  
  RESULTS
  The mean (SD) plasma Lp-PLA(2) concentration for the study participants was 188.7 (41.8) microg/L, with no significant difference between men and women. The analytical CV for Lp-PLA(2) was 4.4%, the within-individual biological CV was 15%, and the between-individual CV was 22%. The ICC was 0.66. An important part of the total variation in plasma Lp-PLA(2) concentration was explained by the between-individual variation (as a percentage of the total variance, 66.1%), whereas the within-individual variance was 31.3%. The analytical variance was as low as 2.6%.
  
  
  CONCLUSIONS
  Between-individual variation in Lp-PLA(2) concentration was substantially greater than within-individual variation. In general, our data demonstrate considerable stability and good reproducibility of serial Lp-PLA(2) measurements, results that compared favorably with those for the more commonly measured lipid markers.
authors.affiliation: Department of Internal Medicine II-Cardiology, University of Ulm Medical Center, Ulm, Germany.
authors.forename: Natalie
authors.initials: N
authors.lastname: Khuseyinova
authors.forename: Sonja
authors.initials: S
authors.lastname: Greven
authors.forename: Regina
authors.initials: R
authors.lastname: Rückerl
authors.forename: Gerlinde
authors.initials: G
authors.lastname: Trischler
authors.forename: Hannelore
authors.initials: H
authors.lastname: Loewel
authors.forename: Annette
authors.initials: A
authors.lastname: Peters
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Koenig
mesh_terms: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000096:biosynthesis*; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000201:enzymology*; D015203:Reproducibility of Results
chemical_list: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase