Underdiagnosis of Heparin-Induced Thrombocytopenia (HIT)

Three factors may help explain the underdiagnosis of HIT:

1.	There is a general lack of awareness[21,30] that may be due, perhaps, to confusion created by the name of the disease, since clinically significant thrombocytopenia (less than 150,000/mcL platelets) may not be present in all patients with HIT.[15,30]
2.	Thrombocytopenia in HIT is paradoxically associated with thrombosis, not with bleeding.
3.	There are a large number of other causes of thrombocytopenia in hospitalized patients (e.g., septicemia/sepsis, hemodilution, disseminated intravascular coagulation, hypercoagulable states, hemodialysis, multisystem organ failure, primary bone marrow disorders, and other concurrent drug therapies).[32]

The diagnosis of HIT should be made first on clinical findings.[17]

Laboratory tests for the diagnosis of HIT are useful; however, they still have limitations. Some laboratory tests are not routinely available for use in the clinical setting.[7,28]