Chemiluminescence immunoassay for sensing lipoprotein-associated phospholipase A2 in cardiovascular risk evaluation

Lipoprotein-associated phospholipase A2 (Lp-PLA₂) is a novel inflammatory biomarker, which is useful as an adjunct identification tool for cardiovascular disease. However, the important limitation of the conventional enzyme-linked immunosorbent assay (PLAC ELISA) for Lp-PLA₂ assay is its relatively low sensitivity and time consuming. A method to measure the Lp-PLA₂ simply, rapidly and sensitively is essential for predicting cardiovascular events in clinic.

We took advantage of magnetic separation integrated with chemiluminescence to detect Lp-PLA₂. The concentration of Lp-PLA₂ was measured through a one-step process by mixing antibody labelled magnetic beads, antigen and antibody at one time.

Our method realized the sample to answer within 17 min. The detection limit and measurement range were 0.18 ng/ml and 0.18-1350 ng/ml, respectively. The specificity assay showed that no appreciable interference was observed for the substances of bilirubin, triglyceride, hemoglobin, rheumatoid factor and human anti-mouse antibody up to the concentrations of 40 mg/dl, 1000 mg/dl, 2000 mg/dl, 1500 IU/ml and 30 ng/ml, separately. We also tested 122 clinical samples using our method, presenting good overall correlations (R² = 0.979) to the PLAC ELISA. It is worth mentioning that, our method was faster, had a wider range of measurement and higher sensitivity compared with the PLAC ELISA.

The Lp-PLA₂ assay is straightforward, sensitive and precise, which is highly suitable to further explore the clinical performance of Lp-PLA₂ in studies of cardiovascular risk management.