The most sensitive tests for confirmation of HIT are functional tests, such as serotonin release assay (SRA) and heparin-induced platelet activa-tion (HIPA), as they only detect antibodies that are capable of activating platelets. Although the enzyme-linked immunosorbent assay (ELISA), which detects PF4/heparin antibodies, is more commonly used, it tends to over-diagnose HIT by also detecting non-pathogenic antibodies.