Heparin-induced thrombocytopenia (HIT) is an immune-mediated complication of heparin treatment. Several in vitro assays are available to detect the causative HIT antibodies: functional assays, usually requiring freshly prepared platelets and immunological tests based on the enzyme-linked immunosorbent assay (ELISA) principle. We compared a new, simple and rapid test based on the ID-microtyping particle agglutination system with 14C-serotonin release assay, heparin-induced platelet activation (HIPA) test and two ELISAs. Sera from 100 confirmed HIT patients, 20 serologically negative suspected HIT patients and 20 healthy blood donors were used. The specificity and sensitivity of the new test was similar to the functional assays. Compared with the ELISAs, specificity was better at the cost of reduced sensitivity. As in all other immunological tests, HIT antibodies against less typical antigens, such as interleukin (IL)-8 or neutrophil-activating peptide (NAP) 2 could not be detected. Thus, although the ID-Heparin/PF4 antibody test seems to be a quick, reliable and robust test to determine the presence of HIT antibodies, it should still be combined with a functional assay if possible. Evaluation of the test in a prospective setting as well as interlaboratory variation should be assessed as a next step.