title: Performance characteristics of an immunoturbidimetric assay for lipoprotein-associated phospholipase A2.
abstract: BACKGROUND
  Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is an inflammatory biomarker for coronary heart disease and ischemic stroke risk assessment.
  
  
  METHODS
  The Plac turbidimetric immunoassay (TIA) for measurement of Lp-PLA(2) was evaluated for limit of blank, functional sensitivity, dilution linearity, imprecision, interferences, and comparison to an ELISA assay for Lp-PLA(2).
  
  
  RESULTS
  The assay was linear from 100 to 500 microg/l. Total inter-assay CVs were <3% for both control levels. Interference studies showed recoveries of 90-110% of expected values at interferent concentrations up to 15 g/l hemoglobin, 450 mg/l bilirubin, and 41 g/l triglycerides. Comparison of 3 sample sets collected using different protocols gave the following regression statistics for the Plac TIA compared to the Plac ELISA: sample set 1 (n=99) slope=1.5, intercept=-122.4, S(y/x)=71.3 microg/l, and r=0.61; sample set 2 (n=100) slope=2.1, intercept=-173 microg/l, S(y/x)=55 microg/l, and r=0.82; sample set 3 after 1 freeze-thaw cycle (n=30) slope=1.2, intercept=-68.6 microg/l, S(y/x)=28.6 microg/l, and r=0.82; sample set 3 after a second freeze-thaw cycle slope=1.4, intercept=-68.2 microg/l, S(y/x)=33.1 microg/l, and r=0.83.
  
  
  CONCLUSIONS
  The Plac TIA reagents perform acceptably on the Roche Modular P analyzer. However, only a fair correlation was observed between the Plac ELISA and Plac TIA assays.
authors.affiliation: ARUP Institute for Clinical & Experimental Pathology, Salt Lake City, UT 84108, United States.
authors.forename: Mindy L
authors.initials: ML
authors.lastname: Rawlins
authors.forename: Sonia L
authors.initials: SL
authors.lastname: La'ulu
authors.forename: Natalie
authors.initials: N
authors.lastname: Moon
authors.forename: William L
authors.initials: WL
authors.lastname: Roberts
mesh_terms: D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase / Q000097:blood*; D000328:Adult; D000368:Aged; D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007202:Indicators and Reagents; D008297:Male; D008875:Middle Aged; D009391:Nephelometry and Turbidimetry / Q000379:methods*
chemical_list: D007202:Indicators and Reagents; D043203:1-Alkyl-2-acetylglycerophosphocholine Esterase