Heparin Induced Thrombocytopenia, ELISA


Abbrev Code:HIT   
Order Code:LAB3532Order Name:Heparin Induced Thrombocytopenia with ELISA
Methodology:ELISA PF4 assay
CPT Codes: 86022 x1, 86022 x1
Turnaround Time:Mon-Fri: If specimen is received by 10 am in the Spec Coag Lab, the test will be done that day. If specimen is received after 10 am in the Spec Coag Lab, the test will be done the next business day.
Associated Links:

Specimen Collection and Processing for Coagulation Specimens



Collection Instructions

Specimen:Blood
Optimal Volume:2.7 mL (in 3 mL tube) - filled to fill line on the tube.
Minimum\Peds Volume:1.8 mL (in 2 mL tube) - filled to fill line on the tube.
Container:Blue Na Citrate, 3.2% - fill to fill line on tube
Alternate Containers: Red (no gel)
Collection Instructions:See link to Specimen Collection and Processing for Coagulation Specimens.
Causes for Rejection:Underfilled tubes, overfilled tubes, clotted specimens, not received or processed and frozen within 4 hours of collection or, specimen thawed during transit.


Processing and Shipping

Specimen Processing:
  • Process for Platelet Poor Plasma within 4 hours of collection.
  • Aliquot plasma, place clear tape around label, and freeze at -20C or on dry ice within 4 hours of collection.
  • If multiple tests are collected on 1 blue top, split each blue top into 2 aliquots. Minimum 0.5 mL per tube.
  • A maximum of 6 aliquots are needed per collection.
     
See link to Specimen Collection and Processing for Coagulation Specimens.
Shipping Instructions:
  • Ensure specimen is frozen before shipping.
  • Ship on dry ice, sample must remain frozen during shipping.
     
See link to Specimen Collection and Processing for Coagulation Specimens.
Test Performed at or Referral Lab UM Special Coag (K)  (UMMC East Bank)


Interpretive

Critical Range:Positive or indeterminate.
Reference Range:Refer to Use field.
Use:

The HIT assay uses the ELISA technique to detect antibodies against the Heparin/Platelet factor 4 complex. The ELISA test used has 2 steps; in the first step (screening test), the presence of HIT antibody is detected with a low concentration of heparin. Since a high concentration of heparin has an inhibitory effect on the antigen and antibody binding, in the second (confirmatory) step, a high concentration of heparin is added during the test to confirm the positive screening result.

 

A positive result requires a positive screening test (O.D. ≥ 0.40) with a low concentration of heparin along with an inhibition of >50% with a high concentration heparin. The test is indeterminate if the screening test is positive (O.D. ≥ 0.40) but the inhibition is <50% in the confirmatory step.

 

Proper interpretation of the lab results with the clinical picture is critical. The ELISA test is very sensitive, but less specific. If there is a discrepancy between the clinical presentation and the laboratory result, the serotonin release assay (send-out test) is recommended for final confirmation or rule out of HIT.

 



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