Flow cytometric assessment of platelet aspirin resistance using light scattering

Background: A simple and reliable assay is needed for the prediction of the clinical efficacy of antiplatelet aspirin therapy. We have devised another method for the evaluation of platelet function and aspirin resistance (AR), via conventional flow cytometry (FCM). Methods: To devise an optimized protocol for the assessment of platelet AR, various analytic variables of FCM were investigated. Using this devised protocol, AR was assessed in healthy subjects as an example. Results: The protocol utilized herein is as follows: citrate-anticoagulated platelet-rich plasma was mixed 1:1 with HEPES-buffered saline in two tubes, one of which is treated with aspirin. During the acquisition of FCM, arachidonate is added to the tube. The response of the aspirin-treated platelets is then compared with those of nontreated ones on a time/forward scatter plot. In the 61 total subjects, none was identified as aspirin resistant by this assay. Conclusions: Using light scattering, platelet aggregation and aspirin's antiplatelet effects can be readily and cost-effectively detected. According to this assay, biochemical AR appears to be rare. This new protocol may prove useful in a clinical setting or as a research tool.