Platelet Function in Paroxysmal Nocturnal Haemoglobinuria

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.4884-4884
• Main Authors: Ayyalil, Fathima Mohiyaddin, Montague, Samantha J, Hicks, Sarah, Kaur, Amandeep, Jahangiri, Anila, Pati, Nalini, Crispin, Philip, Zheng, Yujie, Tienan, Xu, Coupland, Lucy, Lee, Woei Ming, D'Rozario, James, Gardiner, Elizabeth E.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-130291

Introduction Paroxysmal nocturnal haemoglobinuria (PNH) is a rare acquired clonal haematopoietic stem cell disorder characterised by haemolytic anaemia, thrombosis and bone marrow failure. Thrombosis is considered a major cause for high morbidity and mortality in PNH patients (Hillmen P et al N Eng J Med 1995). However, the underlying mechanisms of thrombosis in PNH are still poorly understood. Various factors including defective interactions between the complement system, platelets and coagulation systems have been proposed (Peacock-Young B et al Haematologica 2017). Platelet function and clot formation in this disorder have not been comprehensively evaluated. Here we describe standard and novel techniques to evaluate platelet function in blood from PNH patients, to elucidate the underlying pro-thrombotic mechanisms. Methods Whole blood was collected from five PNH patients and compared to same-day healthy donor (HD) controls. The samples were collected at trough for those patients who were on eculizumab (Complement C5 inhibitor used in the treatment of PNH). Surface levels of platelet adhesion proteins and activation markers P-selectin and phosphatidylserine (PS) were assessed using flow cytometry. Plasma soluble GPVI (a platelet-specific activation marker) and cytokine levels were measured by ELISA. Clot formation was assessed by viscoelastic testing (ROTEM). Adhesion of platelets to collagen under flow in a whole blood assay was evaluated by Digital Holographic Microscopy (DHM) and thrombus height, surface area and volume quantified using custom-built MatLab-based software. Results Clinical characteristics of PNH patients were highly variable: two patients had history of thrombosis, three patients were on eculizumab, four patients were thrombocytopenic (