Background: Platelet aggregation studies using conventional light transmission aggregometry (LTA) have several disadvantages and require strict pre-analytical measures for reliable results.We aimed to examine the utility of flow cytometric platelet aggregation (FCA) assay in detecting platelet function defects (PFDs) in patients with a history of bleeding symptoms. Methods: Sixty-four participants (24 patients and 40 healthy controls) were included in this study.LTA and FCA assay were performed simultaneously in patients and healthy controls. In the FCA assay, two portions of platelets from the same individual were labeled separately with CD31-FITC and CD31-PE. After mixing and stimulation with agonists, the double-colored platelet aggregates were visualized using a flow cytometer. The results generated using the two techniques were compared and correlated. Results: The patients’ median age was 17 years (range, 3‒72 yr) with a male-to-female ratio of 1:1.7. There was substantial agreement between LTA and FCA assay in detecting a PFD (κ=0.792). Four patients showing a Glanzmann thrombasthenia-like pattern on LTA exhibited an abnormal FCA. A functional defect in collagen binding was detected on the FCA assay conducted in two immune thrombocytopenic patients with severe bleeding. Conclusion FCA assay can be used to identify functional defects in platelets, with potential applications in thrombocytopenic individuals. It also facilitates the diagnosis of inherited bleeding disorders with platelet defects.

Background: Platelet aggregation studies using conventional light transmission aggregometry (LTA) have several disadvantages and require strict pre-analytical measures for reliable results.We aimed to examine the utility of flow cytometric platelet aggregation (FCA) assay in detecting platelet function defects (PFDs) in patients with a history of bleeding symptoms. Methods: Sixty-four participants (24 patients and 40 healthy controls) were included in this study.LTA and FCA assay were performed simultaneously in patients and healthy controls. In the FCA assay, two portions of platelets from the same individual were labeled separately with CD31-FITC and CD31-PE. After mixing and stimulation with agonists, the double-colored platelet aggregates were visualized using a flow cytometer. The results generated using the two techniques were compared and correlated. Results: The patients’ median age was 17 years (range, 3‒72 yr) with a male-to-female ratio of 1:1.7. There was substantial agreement between LTA and FCA assay in detecting a PFD (κ=0.792). Four patients showing a Glanzmann thrombasthenia-like pattern on LTA exhibited an abnormal FCA. A functional defect in collagen binding was detected on the FCA assay conducted in two immune thrombocytopenic patients with severe bleeding. Conclusion FCA assay can be used to identify functional defects in platelets, with potential applications in thrombocytopenic individuals. It also facilitates the diagnosis of inherited bleeding disorders with platelet defects.