The assessment of platelet activation in antiplatelet drug development

Platelet activation plays an important role in a wide range of pathological conditions. For example, platelet activation has been shown to be involved in the defence against parasitic infection, the pathogenesis of atherosclerotic disease, and various arterial and venous thrombotic diseases. Indeed, there is considerable interest in the manipulation of platelet function for therapeutic gain. It is for these reasons that there is considerable interest in developing assays measuring in vivo platelet activation. Current modalities in the measurement of platelet activation include Enzyme-linked Immunosorbent Assays (ELISA), platelet flow cytometry and electron microscopy. It is proposed that methods in measuring platelet activation can also be classified into 'direct' and 'indirect' modalities, both of which have their distinct advantages and disadvantages. Unfortunately, there is at present no consensus on the ideal method of measuring platelet activation. Thus, studies on platelet activation should ideally include at least one of each of direct and indirect modality of studying platelet activation. This review provides an overview of basic platelet biology and the various methods of measuring platelet activation, with an emphasis on their role in drug development.