Evaluation of two new automated chemiluminescent assays (HemosIL®AcuStar HIT-IgG and HemosIL®AcuStar HIT-Ab) for the detection of heparin-induced antibodies in the diagnosis of heparin-induced thrombocytopenia

Introduction: Recently, two new, fully automated quantitative chemiluminescent immunoassays, the HemosIL (R) AcuStar HIT-IgG (PF4-H), specific for IgG anti-PF4/H antibodies, and the HemosIL (R) AcuStar HIT-Ab(PF4-H), detecting IgG, IgM and IgA anti-PF4/H antibodies, were introduced into the market. In this study, their performance was compared mutually and with the Zymutest HIA IgG and HIA IgGAM ELISA. Methods: Citrated plasmas from 87 patients with clinical suspicion of heparin-induced thrombocytopenia (HIT) were analyzed with all four assays and with a functional confirmation assay. Apart from the manufacturers cutoffs, optimalized cutoffs were evaluated as well. Results: Sensitivities of all assays were 100%. The Acustar HIT-IgG assay showed a higher specificity compared with the HIT-Ab assay (85%vs. 73%), using the manufacturers cutoffs. Specificities of all assays, except for the AcuStar HIT-IgG, could be significantly improved when altering the cutoff. Titers were significantly higher for the HIT-Ab assay compared with the HIT-IgG assay (P = 0.0001). This was also the case for the patients with confirmed HIT (P = 0.0495), indicating that the one cutoff (1.0 OD) for both Acustar assays, as proposed by the manufacturer, can be adapted for the AcuStar Hit-Ab assay resulting in an increased specificity. Conclusion: Performance characteristics of the Acustar HIT-IgG and HIT-Ab assay are comparable to the Zymutest HIA IgG and HIA IgGAM.