Development of a high-throughput ELISA assay for platelet function testing using platelet-rich plasma or whole blood

Platelets play an essential role in the development of cardiovascular diseases and are the target of several agents that can inhibit their function. Despite the existence of a wide array of techniques to study platelet function, an assay to evaluate several platelet signalling pathways in a high-throughput fashion, combined with minimal blood volume and handling is still needed. We have developed a sensitive assay in the form of a sandwich ELISA where monoclonal antibodies against P-selectin or alphaIIbbeta3 and GPIbalpha were used to capture and detect platelets, respectively, in the presence of five different agonists [ADP, TRAP (thrombin receptor agonist), U46619 (thromboxane A2 analogue), collagen-related-peptide, and arachidonic acid]. Binding of platelets to the antibodies increased dose-dependently with the concentration of either agonist, while binding of ADP-activated platelets was abrogated when inhibitors of platelet activation were concomitantly added. The test showed good sample reproducibility in 15 healthy donors with conserved platelet response to agonists throughout the assay. Healthy subjects could be identified as normal-, hypo- or hyper-responders for each agonist, which for most cases (73%) was confirmed upon retesting. Finally, we demonstrated that the platelet ELISA assay can not only be used in platelet-rich plasma but also in whole blood; it now awaits large scale studies to assess its full screening and diagnostic values.