Summary
Autoimmune thrombocytopenia (ITP) is an acquired autoimmune disease characterised
by isolated persistent thrombocytopenia and normal megakaryopoiesis. This definition
also applies to heparin-induced thrombocytopenia (HIT II), a frequent side effect
of heparin treatment. In HIT II, the immunogen is a coagulation active complex of
heparin and platelet factor 4 (PF4). By now, diagnostics of HIT II is often material
and time consuming. Three groups of patients were investigated for HIT II antibodies
(HIT II-AB): 54 hospitalised stroke patients, 87 hospitalised cardiac patients, and
71 patients on chronic haemodialysis, all treated with heparin. Furthermore, 100 healthy
volunteers were investigated. For detection of HIT II-AB the innovative whole blood
test PADA-HIT (PADA: platelet adhesion assay) was used. PADA-HIT quantifies the interaction
of IgG antibodies with FcγIIA receptors by comparing the activation state of platelets
in citrated and heparinised whole blood. The occurrence of HIT II-AB in blood was
very high with 44 % of stroke patients, 69% of cardiac patients and 38% of haemodialysis
patients compared to only 15% of healthy volunteers. This demonstrates a high incidence
and a rapid onset of HIT II-AB in patients being acutely treated with heparin. HIT
II is one of the most frequent and severe autoimmune diseases bearing a great thrombosis
risk. PADA-HIT represents an innovative diagnostic method for detection of autoimmune
antibodies of IgG type that are directed against platelet factor 4 (PF4)-heparin-complex.
By early and fast diagnostics and appropriate treatment severe complications of HIT
II can be prevented.
Keywords
HIT II - IgG antibody - PADA-HIT - autoimmune disease
