Flow Cytometry-based Functional Assay is a Valuable Diagnostic Approach for Confirmation of Heparin-Induced Thrombocytopenia

Background: Heparin-induced thrombocytopenia (HIT) is a serious immunological adverse drug reaction that rarely occurs in patients receiving heparin.The heparin-induced platelet activation (HIPA) test, a gold-standard assay for HIT, is time-consuming, challenging, and produces qualitative results.We aimed to compare the performance properties of a flow cytometry-based functional assay for HIT diagnosis with HIPA assay. Materials and Methods:This research was carried out on HIT-suspected patients referred to the Iranian Blood Transfusion Organization between 2021 and 2023.After clinical evaluation and 4Ts scores calculation, anti-PF4 screening and HIPA test were conducted.Thirty HIPA-positive and 30 HIPA-negative samples were selected.Subsequently, a flow cytometry-based functional assay, Emo-Test HIT confirm, was performed, and the sensitivity and specificity for HIT diagnosis were measured.Results: Among the 30 samples with negative HIPA results, one was positive with the Emo-test HIT Confirm assay, and the remaining were negative.Among 30 positive HIPA samples, the result of one sample was inconclusive, two samples were negative with flowcytometry Emo-test and the others were positive.The sensitivity and specificity of this flow cytometry-based functional assay were 90% (95% CI: 79.3-100) and 96.6% (95% CI:90.2-100).The negative predictive value and positive predictive value were 93.5% and 96.4% respectively. Conclusion:Flow cytometry-based functional assay has a good sensitivity and specificity for HIT diagnosis confirmation, indicating that it may be a promising approach in the clinical setting.