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 i mmunglobulin classes can be used to differentiate between antibody-positive patients with and without HIT. Four different patient populations were inv estigated: 32 patients with the immune type of HIT with thromboembolic comp lications, 13 patients with HIT without thromboembolism, 24 patients with h eparin-platelet factor 4 (PF4) antibodies without clinical symptoms of HIT and 20 heparin-treated patients with thrombocytopenia caused by other reaso ns, 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 complic ations and patients with isolated HIT were found concerning the different i mmunglobulin classes. Antibody-positive patients with KIT had significantly higher levels of IgG antibodies than those without HIT (P < 0.05), while t hey did not differ concerning IgM and IgA antibodies. By determining IgG an tibodies, the specificity of the enzyme-linked immunosorbent assay (ELISA) system was increased without loss of sensitivity Heparin-PF4-IgG antibodies can identify patients at risk of developing life-threatening HIT. Future E LISAs should only include this immunglobulin class, as the determination of the antibody mixture may lead to overestimation of HIT.