What is the role of immunoassays in the workup of heparin-induced thrombocytopenia (HIT)?

Updated: Sep 10, 2021
  • Author: Sancar Eke, MD, FASN; Chief Editor: Srikanth Nagalla, MD, MS, FACP  more...
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Immunoassays include solid-phase immunoassays (heparin/PF4 enzyme-linked immunosorbent assay [ELISA]), and particle gel immunoassays. Immunoassays are widely available and have a rapid turnaround time and high sensitivity (> 99%). However, they have poor specificity (30%-70%) because they also detect nonpathogenic antibodies. [49]

The specificity of ELISA can be enhanced by taking into account the optical density of the result. Higher absolute optical density values correlate with a clinical diagnosis of HIT. Warkentin and colleagues reported that weaker optical density values (0.4 to <1.00) indicated a 5% or lower probability of a strongly positive result on functional testing with the serotonin release assay (SRA), whereas an optical density value of 2.0 or more resulted in an approximately 90% probability of a strong SRA result. [50]

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