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 (R) 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 mu g/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 mu g/l, and r = 0.61; sample set 2 (n = 100) slope = 2.1, intercept = -173 mu g/l, S-y/x = 55 mu g/l, and r = 0.82; sample set 3 after 1 freeze-thaw cycle (n = 30) slope = 1.2, intercept = -68.6 mu g/l, S-y/x = 28.6 mu g/l, and r = 0.82; sample set 3 after a second freeze-thaw cycle slope = 1.4, intercept = -68.2 mu g/l, S-y/x = 33.1 mu g/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. (C) 2009 Elsevier B.V. All rights reserved.