Lp-PLA2 (Lipoprotein-associated phospholipase A2)

Lp-PLA2 (platelet-activating factor acetylhydrolase) is a calcium-independent enzyme secreted mainly by macrophages and lymphocytes; in plasma roughly 80% circulates bound to LDL, where it hydrolyses oxidised phospholipids on retained LDL particles to release lysophosphatidylcholine and oxidised fatty acids, both proinflammatory in the arterial wall. It is measured by mass (immunoassay, the FDA-cleared PLAC test, with values above approximately 200-225 ng/mL considered elevated) or by activity assay (cutoff approximately 225 nmol/min/mL). The Lp-PLA2 Studies Collaboration meta-analysis (Thompson 2010, 79,036 participants) reported a risk ratio of 1.10-1.11 per standard deviation increment for coronary heart disease and ischaemic stroke, comparable to non-HDL cholesterol. Major confounders include statins (lower Lp-PLA2 by approximately 20-30%), fibrates, ezetimibe, weight loss, and the rare loss-of-function PLA2G7 V279F variant common in East Asian populations.