Ordering Recommendation

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




1-2 days

New York DOH Approval Status

This test is New York DOH approved.

Specimen Required

Patient Preparation

Serum separator tube.

Specimen Preparation

Separate from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.2 mL)

Storage/Transport Temperature

CRITICAL FROZEN. Additional specimens must be submitted when multiple tests are ordered.

Unacceptable Conditions

Heparinized specimens.


Ambient: Unacceptable; Refrigerated: 48 hours; Frozen: 2 years

Reference Interval

Less than or equal to 0.399 OD

Interpretive Data

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.

Compliance Category



Microbially contaminated, heat-inactivated, hemolyzed, icteric, or lipemic sera may give inconsistent results.

Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
2012180 Hep-Ind Thrombocytopenia PF4 Ab, IgG 73818-7
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • HAT
  • Heparin Induced Antibodies
  • Heparin PF4 Antibody
  • Heparin-Associated Antibody
  • HIPA
  • HIT Antibodies
  • HIT IgG, IgM, IgA
  • HIT PF4 Antibodies
  • HITA
  • Type II HIT
Heparin-Induced Thrombocytopenia (HIT) PF4 Antibody, IgG