Heparin-Induced Thrombocytopenia (HIT) PF4 Antibody, IgG with Reflex to Serotonin Release Assay (Heparin Dependent Platelet Antibody), Unfractionated Heparin

This ELISA assay detects the presence of IgG antibodies to heparin-platelet factor 4 (PF4) complexes. Most cases of heparin-induced thrombocytopenia (HIT) are caused by IgG antibodies to heparin-PF4, rather than IgA or IgM antibodies. Negative results have a good negative predictive value for HIT, although rare false-negative results may occur. Positive ELISA results are sensitive but not completely specific for HIT. HIT is a clinicopathologic diagnosis. Clinical findings and the results of other laboratory tests must be taken into consideration. Higher optical density (OD) values in the IgG ELISA test correlate with a higher likelihood of positivity in platelet activation assays, such as the serotonin release assay (SRA), and an increased likelihood of clinical HIT.

A clinical scoring system to assess pretest probability of HIT along with other guidance for diagnosis is available in ARUP Consult®: https://www.arupconsult.com/content/heparin-induced-thrombocytopenia.

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.