Advantages of the lipoprotein-associated phospholipase A2 activity assay

Objectives: Lipoprotein-associated phospholipase A2 (Lp-PLA(2)) is increased in circulation in patients at higher risk of coronary heart disease (CHD) events and stroke. Therefore, measurement of Lp-PLA(2) 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-PLA(2) activity (diaDexus, San Francisco, CA) received FDA approval. Here we evaluate the assay performance of the Lp-PLA(2) activity assay. Methods: Lp-PLA(2) 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 (0-400 nmol/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 7.8 nmol/min/mL with an average %CV of 2.8%. Precision studies revealed a coefficient of variation <= 1.6% between 79 and 307 nmol/min/mL and accuracy was demonstrated between 4.8-368.7 nmol/min/mL. Comparable results were generated in paired SST serum and EDTA plasma. No age association was found with Lp-PLA(2) 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-PLA(2) activity results are extremely stable in both serum and EDTA plasma under refrigerate and frozen storage conditions up to 31 days. Conclusions: Lp-PLA(2) 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-PLA(2) activity in clinical practice. (C) 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.