Recommended initial screening test for heparin-PF4 antibodies that cause HIT. Confirmation with Serotonin Release Assay (Heparin Dependent Platelet Antibody), Unfractionated Heparin (2005631) may be necessary based on clinical presentation.
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Serum separator tube.
Separate from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.2 mL)
CRITICAL FROZEN. Additional specimens must be submitted when multiple tests are ordered.
Ambient: Unacceptable; Refrigerated: 48 hours; Frozen: 2 years
Less than or equal to 0.399 OD
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.
Microbially contaminated, heat-inactivated, hemolyzed, icteric, or lipemic sera may give inconsistent results.
|Component Test Code*||Component Chart Name||LOINC|
|2012180||Hep-Ind Thrombocytopenia PF4 Ab, IgG||73818-7|
- Heparin Induced Antibodies
- Heparin PF4 Antibody
- Heparin-Associated Antibody
- HIT Antibodies
- HIT IgG, IgM, IgA
- HIT PF4 Antibodies
- Type II HIT