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Growing evidence supports a role for extracellular vesicles (EVs) in haemostasis and thrombosis due to exposure of negatively charged procoagulant phospholipids (PPL). Current commercial PPL-dependent clotting assays use chemically phospholipid depleted plasma to measure PPL activity. The purpose of our study was to modify the PPL assay by substituting the chemically phospholipid depleted plasma with PPL depleted plasma obtained by ultracentrifugation This in order to get readily access to a sensitive and reliable assay to measure PPL activity in human plasma and cell supernatants. The performance of the assay was tested, including the influence of individual coagulation factors and postprandial lipoproteins and compared to a commercial PPL assay (STA-Procoag-PPL). The two PPL assays displayed similar sensitivity to exogenously added standardized phospholipids. The PPL activity measured by the modified assay strongly correlates with the results from the commercial assay. The intraday- and between-days coefficients of variation ranged from 2-4% depending on the PPL activity in the sample. The modified PPL assay was insensitive to postprandial lipoprotein levels in plasma, as well as to tissue factor (TF) positive EVs from stimulated whole blood. Our findings showed that the modified assay performed equal to the comparator, and was insensitive to postprandial lipoproteins and TF + EVs.

Conflicting results have been reported about the absorption of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) either as an ethyl ester (EE) or in a triglyceride (TG) formula. We decided to conduct a randomized double-blind study to compare the effects of EE and TG on plasma fatty acids, platelet function and haemostasis. Thirty-one healthy normolipaemic men were allocated to receive fish oil concentrate either as EE or TG with equal amounts of EPA (2.2 g and 2.2 g, respectively) and DHA (1.2 g and 1.4 g, respectively) or placebo daily for 7 weeks. Total cholesterol and the triglyceride level were not influenced differently by the two compounds. Repeated measurement ANOVA revealed a difference between TG and EE regarding incorporation of arachidonic acid (P = 0.034) and EPA (P = 0.007) into plasma cholesteryl esters. A discrimination not observed within plasma phospholipids. Both formulas had equal inhibitory effects on collagen-induced platelet aggregation and thromboxane B2 (TxB2) production in whole blood. Fibrinogen decreased 16% in EE (P = 0.034) and 12% in the placebo group (P = 0.11), but variance analysis of delta change during intervention did not indicate differences between groups. It is concluded that TG and EE fish oils are well incorporated into plasma lipids and have similarly beneficial influence one platelet function in men.