Determination of heparin–platelet factor 4–IgG antibodies improves diagnosis of heparin‐induced thrombocytopenia

Only a few patients with heparin‐induced antibodies develop heparin‐induced thrombocytopenia (HIT). In this study, we investigated whether different immunglobulin classes can be used to differentiate between antibody‐positive patients with and without HIT. Four different patient populations were investigated: 32 patients with the immune type of HIT with thromboembolic complications, 13 patients with HIT without thromboembolism, 24 patients with heparin–platelet factor 4 (PF4) antibodies without clinical symptoms of HIT, and 20 heparin‐treated patients with thrombocytopenia caused by other reasons. In all patients the immunglobulin mixture of IgG, IgM and IgA, and the single immunglobulin classes of heparin–PF4 antibodies, were investigated. No significant differences between HIT patients with thromboembolic complications and patients with isolated HIT were found concerning the different immunglobulin classes. Antibody‐positive patients with HIT had significantly higher levels of IgG antibodies than those without HIT (P