Proposed Role of Thromboelastometry Assay in Discerning Coagulation Pattern of Patients Suffering Immune-Mediated Thrombocytopenia

Platelet-derived antigens can trigger immune-mediated responses, the most common of which is heparin-induced thrombocytopenia (HIT). IgG antibodies to platelet factor 4 (PF4)-heparin complexes trigger the clinical manifestations of HIT. Only a subset of these antibodies will activate platelets and release of platelet-derived microparticles (PMPs), which heightened thrombin generation (TG) and fibrin polymerization leading to modify fibrin network structure. All together result in heparin-induced thrombosis/thrombocitopenia (HITT). The effectiveness of HIT laboratory testing by means of immunoassays is largely dependent on the method used whereas functional tests, which can demonstrate the platelet-activating properties of HIT-antibodies are currently limited to a few laboratories. We present 3 patients with suspected diagnosis of HIT. Thromboelastometry (ROTEM®) assay, with the first derivative of the clot growth velocity curve (V-curve) variables, was used for rapid differential diagnosis. Despite of standard variables similarity, the V-curve differed in the 3 patients. In the patient who developed HITT, the V-curve showed an exceptionally high maximum velocity of fibrin formation (22 mm s-1) with a critically low maximal lysis (1%), suggesting procoagulant state, whereas these values were normal (10 mm s-1 and 12% respectively) in the patient without HITT. In the patient with a definitive diagnosis of irofiban-induced severe thrombocitopenia, maximum velocity of fibrin formation was markedly low (5 mm s-1), with moderate hyperfibrinolysis (21%) indicating hypocoagulable state. In patients suffering from immune-mediated thrombocytopenia viscoelastic assays could provide useful information.