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Heparin Induced Thrombocytopenia (HIT) Antibody Testing

Item Value
Approval req'd? No, but if "washed platelet-heparin induced platelet activation" is required before result of heparin-PF4 ELISA test is available, please contact hematology at x3-1747
Available Stat? No
Utilization Guidelines The pretest likelihood of HIT can be assessed by the 4T's:

Category 2 points 1 point 0 points
Degree of thrombocytopenia Fall > 50% and nadir ≥ 20K fall 30-50% or nadir 10K-19K Fall < 30% or nadir < 10K
Timing of fall 5-14 days post heparin or ≤ 1 day if prior exposure < 30 days Consistent with days 5-14 fall, but not clear or onset after day 14 or fall ≤ 1 day (with heparin exposure 30-100 days ago) ≤ 4days without recent exposure
Thrombsis or sequelae New thrombosis; skin necrosis; acute systemic reaction post IV unfract. heparin Progressive or recurrent thrombosis; skin erythema w/out necrosis; suspected thrombosis only (not confirmed) None
Other cause of thrombocytopenia None apparent Possible Definite

Score Probability of HIT
1-3 Low
4-5 Intermediate
6-8 High

Adapted from: American Society of Hematology Guideline, 2009 Clinical Practice Guideline on the Evaluation and Management of Heparin-Induced Thrombocytopenia.
Test code HEPAB
Test group HIT
Performed by Machaon Diagnostics
Sendout? Yes
Method Enzyme Linked Immunosorbent Assay
Container type Red top
Amount to Collect 2 mL blood
Sample type Serum
Preferred volume 1 mL serum
Min. Volume 0.5 mL serum
Processing notes Deliver specimen immediately to Hematology M524 for processing.

Hematology: Freeze serum at -20C. Order Machaon test "heparin pf4 w/ reflex to wp-HIPA".

If the Reflex test for wp-HIPA is required, the test code HEPWP will be ordered to bill the additional charge when the results are entered at China Basin.
Ref Lab Rejection Criteria Sample thawed on receipt
Normal range
Heparin antibody by Elisa Negative
wp-HIPA Normal
Synonyms HIT; heparin induced thrombocytopenia; platelet factor 4; HIT panel; platelet factor 4; HPA; heparin induced platelet antibody; HIPAB; SRAU; Serotonin Release Assay
Stability Frozen 7 days
Turn around times 1-2 days
Reflex? A heparin antibody by ELISA method will be performed initially. If results are positive, will reflex to a washed platelet heparin-induced platelet activation method (wp-HIPA).
Additional information A negative test does not exclude thrombotic risk due to heparin induced thrombocytopenia (HIT), nor does a positive test exclude other causes of thrombocytopenia. Correlation with wp-HIPA, platelet counts, and clinical findings can be important for diagnosis of HIT.

Antibodies to heparin-PF4 complexes are found in the majority of patients with clinical findings of heparin-induced thrombocytopenia (HIT), but also in variable numbers of heparinized patients without thrombocytopenia.

For assistance in interpreting results, please contact the Hematology consultation services: for adults pager 443-4276, for pediatrics pager 443-6966. Or you may contact Hematology lab resident at 353-1747.
CPT coding 83520-90 (HEPAB), 86022-90 x3 (HEPWP)
LOINC code 45155-9 (HEPAB), 50736-8 (HEPWP)
Last Updated 1/14/2016 9:43:39 AM
Entry Number 1654
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