HEPARIN-ASSOCIATED THROMBOCYTOPENIA - NO ASSOCIATION OF IMMUNE-RESPONSE WITH HLA

Heparin-associated thrombocytopenia (HAT) is a severe adverse reaction of heparin therapy. Patients with the immunologic type of HAT are at risk of developing arterial and venous thromboembolic complications ca used by an antibody which activates platelets in the presence of hepar in. Yet, there are no means to identify patients at risk of developing HAT before heparin administration. We investigated the frequency of H LA class-I and class-II antigens in 47 patients with the immunologic t ype of HAT verified by a positive two-point heparin-induced platelet a ctivation assay. Compared to a control group of 629 healthy individual s HLA antigens B8 and DR3 were less frequent, whereas DR4 and DR53 had a higher frequency. However, none of these antigens proved to be stat istically significant. This is another example of an immunologically m ediated disease showing no discernible association with the HLA system .