What is a heparin-induced platelet aggregation assay (HIPAA), and what is its role 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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HIPA is a platelet-activation test in which the patient's serum is mixed with donor platelets in the presence of heparin. Aggregation of the donor platelets indicates the presence of antibodies to the heparin–PF4 complex. Chong and colleagues reported that the mean sensitivity of HIPA may vary from 39% to 81%, depending on the heparin concentration and the reactivity of the platelets used, while specificity ranged from 82-100%. [56]

HIPA proved to be more sensitive than PF4 ELISA for laboratory confirmation of HIT, in a study involving serum samples from 146 patients examined for HIT. However, neither the HIPA nor the PF4 ELISA predicted thrombotic risk.

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