[EXPERIENCE IN DIAGNOSTIC ASSAYS FOR HEPARIN-INDUCED THROMBOCYTOPENIA - EXPERIENCE OF A TERTIARY HOSPITAL IN ISRAEL].

AIMS: To analyze the experience of a tertiary medical center in clinical and laboratory diagnosis of suspected HIT. BACKGROUND: The diagnosis of heparin-induced thrombocytopenia (HIT) requires clinical data and laboratory detection of platelet activating factor 4/heparin (PF4/H) antibodies by immunological or functional assays. Although antigen screening assays are widely used, the functional assays are performed only by several expert labs. METHODS: A retrospective review of the Hematology Laboratory database on patients evaluated between the years 2008-2016 at Rambam, identified 412 individuals with clinical suspicion of HIT. Till 2011, 135 cases were screened using particle gel PaGIA (Biorad) and between the years 2012-2016, a total of 277 cases were screened by lateral flow Milenia (Biotec GmbH). All patients diagnosed with HIT were treated with Fondaparinux (Arixtra). Functional assay with heparin/LMWH induced platelet aggregation was performed using light transmission aggregometry (Helena AggRAM) to validate borderline or positive results in indistinct cases. RESULTS: From the tested samples, 63% vs. 75% were negative in PaGIA and Milenia, respectively (P=0.03), and were considered negative for HIT. During 2008-2011, only 38% of cases with non-negative immunoassay results underwent functional aggregation, whereas, in 2012-2016, 83% of such cases were further evaluated. None of the borderline PaGIA samples was positive in the functional assay compared to 13.3% borderline Milenia results; 25% of positive PaGIA and 51.7% of positive Milenia were confirmed by a positive functional HIT assay (P=N.S.). The survival rate among 14 patients with a positive functional assay was 42.7 % (6 patients). CONCLUSIONS: The Milenia assay introduced at our lab in 2012, has improved the screening process. The functional assay provides a more accurate HIT diagnosis. The combined approach of an optimal laboratory and clinical investigation is crucial to obtain a precise HIT diagnosis.