Step Clinical and Lab. assessment Action plan
1 suspicion of HIT thrombocytopenia (<150×109 /L, unexplained decrease of > 30%), timing of over 5 days, no other cause of thrombocytopenia or thrombosis
2 ELISA (IgG, A, M) no likelihood of HIT due to a negative qualitative assay
3 specific IgG-ELISA high specificity for platelet-activating antibodies
4 14C serotonin release assay
(platelet aggregation test)
confirmation of HIT as a gold standard test
(not preferable due to being less sensitive)
5 reassessment of HIT if necessary recheck other causes of thrombocytopenia and thrombosis, assess with alternative therapy
Table 1: Diagnostic approach to HIT.