Attaphon ChamchoiSirada SrihirunKittiphong PaiboonsukwongThanaporn SriwantanaPeerawich KongkaewSuthat FucharoenKovit PattanapanyasatNathawut SibmoohMahidol UniversityFaculty of Medicine, Siriraj Hospital, Mahidol University2020-08-252020-08-252020-01-01International Journal of Laboratory Hematology. (2020)1751553X175155212-s2.0-85086436705https://repository.li.mahidol.ac.th/handle/20.500.14594/57751© 2020 John Wiley & Sons Ltd Introduction: An increase in platelet activity is a contributing factor to vascular complications in hemoglobin E/β-thalassemia (HbE/β-thal). Plasma-free hemoglobin (Hb) increases in HbE/β-thal patients and correlates with platelet activation, but the levels of Hb-bound platelets have never been reported. In this study, we aimed to investigate the levels of Hb-bound platelets and its association with platelet activity in HbE/β-thal patients. Methods: Hb-bound platelets were measured by flow cytometry in 22 healthy subjects and 26 HbE/β-thal patients (16 nonsplenectomized and 10 splenectomized HbE/β-thal patients). Plasma Hb was measured by the chemiluminescence method based on the consumption of nitric oxide (NO) by Hb. Expression of P-selectin and activated glycoprotein (aGP) IIb/IIIa on platelets was measured by flow cytometry as a marker of platelet activity. Results: Both nonsplenectomized and splenectomized HbE/β-thal patients had higher levels of Hb-bound platelets and plasma Hb than healthy subjects. In vitro incubation of dialyzed Hb from patients with platelets of healthy subjects caused an increase in Hb-bound platelets, which was partially inhibited by anti-GPIbα antibody. Plasma Hb positively correlated with Hb-bound platelets. Platelet P-selectin expression at baseline and in response to adenosine diphosphate (ADP, 1 µM) stimulation was higher in nonsplenectomized and splenectomized HbE/β-thal patients than healthy subjects. The ADP-induced aGPIIb/IIIa expression on platelets was also higher in HbE/β-thal patients than healthy subjects. Hb-bound platelets correlated with baseline P-selectin expression and ADP-induced P-selectin expression. Conclusion: HbE/β-thal patients have increased Hb-bound platelets, which is associated with increased baseline platelet activation and reactivity.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyMedicineArticleSCOPUS10.1111/ijlh.13260