Background : This study was purposed to establish reference values for platelet activation markers and leukocyte-platelet aggregates in the evaluation of the platelet function tests using flow cytometry.
Methods : Whole blood samples were obtained from 30 volunteers of healthy adults. Diluted blood samples, either in the resting state or in activated state by the addition of agonist, 20 μM ADP or 100 μM TRAP, were stained with fluorescent conjugated monoclonal antibody of PAC1 or CD62P. Then, the percentages of expression for each marker were analyzed by flow cytometry. For leukocyte-platelet aggregates, monoclonal antibodies of CD41a, CD14 and CD45 were added simultaneously to undiluted whole blood.
Results : Reference values for the percentages of the expression of PAC1 and CD62P, respectively,were 0.1-12.5% and 0.0-4.7% at the resting state, 65.3-92.4% and 39.0-75.7% with the addition of 20 μM ADP, and 68.1-93.1% and 60.5-91.2% with the addition of 100 μM TRAP. Reference values for leukocyte-platelet aggregates, granulocyte-platelet aggregates, and lymphocyte-platelets aggregates were 2.8-23.6%, 5.3-34.2%, and 4.9-21.6%, respectively.
Conclusions : The platelet activation markers at the resting or an activated state with agonists and leukocyte-platelet aggregates could be analyzed using flow cytometry. These reference values should be helpful in interpreting platelet function tests by flow cytometry.

Keywords: Platelet activation, Reference values, Flow cytometry, Leukocyte-platelet