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Subject: Heparin-Induced Thrombocytopenia (HIT) Assays
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HIT refers to thrombocytopenia that develops during or following the administration of heparin. There are various assays in use, none entirely satisfactory.
There are two groups of assays:
Immunologic: ELISA assays: use specific IgG antibodies; these assays have a high negative and positive predictive value.
Functional: Serotonin release assay, the gold standard for diagnosing HIT. An alternative functional assay is platelet aggregation standardized to use heparin as the aggregating agent.
ELISA: negative if <0.4 optical density
Serotonin release assay (depends on the laboratory's own methodology): negative or positive
An HIT assay should be performed whenever HIT is clinically suspected.
ELISA requires well-trained, experienced technologists for accurate performance.
Serotonin release requires the use of radioactive materials. It is performed in only a few reference laboratories.