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.

New York DOH Approval Status

This test is New York state 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


Semi-Quantitative Enzyme-Linked Immunosorbent Assay




1-2 days

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