This invention relates to a method of analyzing coagulative, fibrinolytic or haemostatic activity in, especially, blood or plasma from mammals, particularly humans. The method comprises bringing a sample, in vitro, into contact with fixed and preferably from their growth support detached endothelial cells or outer membranes of such cells, and detecting the resulting coagulated material and, in some cases, lyzed coagulated material. Reagents are also described that are based on the endothelial cells and their outer membranes. A kit for performing such a method including the claimed reagent is also described.