title: Biological variability of lipoprotein-associated phospholipase A2activity in healthy individuals.
abstract: OBJECTIVE
  Measuring lipoprotein-associated phospholipase A2(Lp-PLA2) activity can aid in identifying individuals at higher risk of coronary heart disease. However, the biological variation of Lp-PLA2activity and corresponding reference change value (RCV) is unknown which limits interpretation of results. In this study we aim to define the intra- and inter-individual variability of Lp-PLA2activity in a healthy reference population.
  
  
  METHODS
  A total of 24 healthy individuals (22-47years of age) were prospectively collected at several time points: daily for five days (after overnight fast), daily for three days (while non-fasting), weekly for four weeks (after overnight fast), and monthly for 6months (after overnight fast). Intra-individual and inter-individual variability was determined. The index of individuality (IoI) and reference change value (RCV) were calculated for each time period.
  
  
  RESULTS
  Variability in Lp-PLA2activity was not different in fasting versus non-fasting states and also did not change in daily versus monthly testing. The RCV for monthly Lp-PLA2activity was found to be 17%. More than 90% of the variability was attributable to between person differences while analytic variability comprised <9% of the variability and within-person variability was low at <0.7%. The index of individuality for monthly testing was 0.30 CONCLUSIONS: In a healthy population, Lp-PLA2activity displays low analytical and within-person variability and higher inter-individual variability. The change required to differentiate a true change in patient status was determined to be 17% for monthly measurements. The between individual variability and corresponding RCV for the activity assay are lower than previously reported results for the Lp-PLA2mass assay.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, United States. Electronic address: donato.leslie@mayo.edu.
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Donato
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Meeusen
authors.affiliation: Department of Health Sciences Research, Mayo Clinic, Rochester, MN, United States.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Jenkins
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Stacy J
authors.initials: SJ
authors.lastname: Hartman
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, United States.
authors.forename: Amy K
authors.initials: AK
authors.lastname: Saenger
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Nikola A
authors.initials: NA
authors.lastname: Baumann
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Darci R
authors.initials: DR
authors.lastname: Block
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, United States; Department of Cardiology, Mayo Clinic, Rochester, MN, United States.
authors.forename: Allan S
authors.initials: AS
authors.lastname: Jaffe
mesh_terms: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000097:blood*; D000328:Adult; D015415:Biomarkers / Q000097:blood*; D003324:Coronary Artery Disease / Q000097:blood / Q000175:diagnosis* / Q000201:enzymology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D011379:Prognosis; D011446:Prospective Studies
chemical_list: D015415:Biomarkers; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase
keywords: Index of individuality; Lipoprotein-associated phospholipase A(2); Lp-PLA(2); PLAC activity; Platelet activating factor acetylhydrolase; RCV; Reference change value