Procoagulant Phospholipid Activity, Whole Blood Thromboelastography and Thrombin Generation Assay to Detect Hypercoagulability in Thalassemic Children

INTRODUCTION: Life expectancy of thalassemia patients has markedly increased over the last few decades. Nevertheless patients suffer from many complications of this congenital chronic disease.The presence of a highincidence of thrombotic events has led to the identification of a hypercoagulable state in these patients.The thrombotic risk is higher in β-thalassemia intermedia and splenectomized patients. The mechanisms responsible for the increased thrombotic risk are still unclear. Several factors that contribute to the hypercoagulable state in patients with thalassemia have been identified: chronic platelet activation, abnormal red blood cells, microparticles,iron overload, endothelial damage, splenectomy, decreased levels of anticoagulant factors and presence of prothrombotic mutations. We aimed to assess hypercoagulability in children with β-thalassemia.

DESIGN AND METHODS: Sixty eight thalassemia major and 42 thalassemia intermedia patients included our study. The control group consisted of 41 age and sex matched healthy children. Demographic data of patients were recorded from their medical records. None of the thalassemic patients have thrombosis before. To evaluate the relative role of microparticles, blood cells and plasma: coagulation tests (prothrombin time, activated prothrombin time, fibrinogen and d-dimer), serum coagulation factor levels (factor II, V, VII, VIII, IX, X, von willebrand factor, protein C, protein S, antithrombin III), procoagulant phospholipid activity and thrombin generation assay were studied from plasma, thromboelastography from whole blood.

The main component of microparticles are negative anionic phospholipids.Procoagulant phospholipid activity is a functional analyse to detect microparticles.Thromboelastography measures indices of the viscoelastic properties of whole blood after activation of coagulation and the thrombin generation assay measures the actual thrombin concentrations before and after the clot is formed.

RESULTS: The median age is 144 months ( 11-236 months)in thalassemia major and 142 months (72-202 months) in thalassemia intermedia patients. Plasma factor II, factor V, factor IX, factor X and protein C levels were significantly lower in thalassemia major and intermedia patients than control subjects. Plasma phospholipid activity and whole blood thromboelastography parameters were all consistent with hypercoagulability in thalassemic patients, especially in splenectomized patients. Endogenous thrombin potential (area under the curve in thrombin generation assay) was significantly lower in thalassemic patients than control subjects and in non-splenectomized patients than splenectomized patients contrary to expectations.

CONCLUSIONS: The hypercoagulability in thalassemic patients especially in splenectomized patients can be determined with procoagulant microparticle activity and whole blood thromboelastography but not with thrombin generation assay in platelet poor plasma. These findings showthat blood cells and/or platelets may be more important determinants of thrombotic risk rather than plasma abnormalities in thalassemic patients.