title: Advantages of the lipoprotein-associated phospholipase A2 activity assay.
abstract: OBJECTIVE
  Lipoprotein-associated phospholipase A2 (Lp-PLA2) is increased in circulation in patients at higher risk of coronary heart disease (CHD) events and stroke. Therefore, measurement of Lp-PLA2 can be used as an adjunct to traditional cardiovascular risk factors for identifying individuals at higher risk of cardiovascular events. Recently, a reagent for measuring Lp-PLA2 activity (diaDexus, San Francisco, CA) received FDA approval. Here we evaluate the assay performance of the Lp-PLA2 activity assay.
  
  
  METHODS
  Lp-PLA2 activity assay reagent performance was evaluated on an open user-defined channel on a Cobas 6000/c501 (Roche Diagnostics, Indianapolis, IN) using a 5-point calibration curve (0-400nmol/min/mL). Analytical performance was established for the following parameters: precision, linearity, accuracy, analytical sensitivity, analytical specificity, reference interval, reagent lot-to-lot comparison, specimen type, on-board reagent stability, and sample stability.
  
  
  RESULTS
  Assay limit of detection was determined to be 7.8nmol/min/mL with an average %CV of 2.8%. Precision studies revealed a coefficient of variation ≤1.6% between 79 and 307nmol/min/mL and accuracy was demonstrated between 4.8-368.7nmol/min/mL. Comparable results were generated in paired SST serum and EDTA plasma. No age association was found with Lp-PLA2 activity at the 95th percentile however a gender association was identified resulting in gender-specific 95th percentile limits in a healthy reference population. No bias was found when comparing results from several different lots of assay reagent. Lp-PLA2 activity results are extremely stable in both serum and EDTA plasma under refrigerate and frozen storage conditions up to 31days.
  
  
  CONCLUSIONS
  Lp-PLA2 activity assay displays accurate and precise performance characteristics on the Cobas c501 platform. The assay performance is significantly improved over the predecessor immunoassay allowing for adoption of Lp-PLA2 activity in clinical practice.
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 Laboratory Medicine and Pathology Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Heidi
authors.initials: H
authors.lastname: Callanan
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, 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; Division of Cardiology, Mayo Clinic, Rochester, MN 55905, United States.
authors.forename: Allan S
authors.initials: AS
authors.lastname: Jaffe
mesh_terms: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000097:blood*; D003327:Coronary Disease / Q000097:blood*; D006801:Humans; D057230:Limit of Detection; D020521:Stroke / Q000097:blood*
chemical_list: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase
keywords: Assay validation; Biomarkers; Lipoprotein-associated phospholipase A2; Lp-PLA(2); PLAC activity; Platelet activating factor acetylhydrolase