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Heparin-Induced Thrombocytopenia (HIT) PF4 Antibody, IgG
2012179
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.

Mnemonic
HIT IGG
Methodology
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Performed
Sun-Sat
Reported
1-2 days
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
 
Collect
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. 
Remarks
 
Stability
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®: http://www.arupconsult.com/Topics/HIT.html.

Note
Microbially contaminated, heat-inactivated, hemolyzed, icteric, or lipemic sera may give inconsistent results.
Components
Component Test Code*Component Chart NameLOINC
2012180Hep-Ind Thrombocytopenia PF4 Ab, IgG73818-7
* 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.
Aliases
  • HAT
  • Heparin Induced Antibodies
  • Heparin PF4 Antibody
  • Heparin-Associated Antibody
  • HIPA
  • HIT Antibodies
  • HIT IgG, IgM, IgA
  • HIT PF4 Antibodies
  • HITA
  • Type II HIT