Ordering Recommendation

Gold standard reflex testing for confirming diagnosis of HIT. Serotonin Release Assay is performed for positive HIT Antibody, IgG.

Mnemonic
HIT G RFLX
Methodology

Semi-Quantitative Enzyme-Linked Immunosorbent Assay/Serotonin Release Assay

Performed

Sun-Sat

Reported

1-6 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Serum separator tube.

Specimen Preparation

Separate from cells ASAP or within 2 hours of collection. Transfer 5.0 mL serum to an ARUP Standard Transport Tube. (Min: 2.0 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
Test Number Components Reference Interval
2012179 Heparin-Induced Thrombocytopenia (HIT) PF4 Antibody, IgG Less than or equal to 0.399 OD
2005631 Serotonin Release Assay (Heparin Dependent Platelet Antibody), Unfractionated Heparin Negative

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/content/heparin-induced-thrombocytopenia.

Compliance Statement B: For laboratory developed tests not using a RUO kit, and for FDA approved, cleared or 510(k) exempt assays with alterations. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.

Note

Microbially contaminated, heat-inactivated, hemolyzed, icteric, or lipemic sera may give inconsistent results. If Heparin-Induced Thrombocytopenia (HIT) PF4 Antibody, IgG is 0.400 O.D. or greater, Serotonin Release Assay (Heparin Dependent Platelet Antibody), Unfractionated Heparin is added. Additional charges apply.

Hotline History
N/A
CPT Codes

86022; if reflexed, add 86022

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