Using an ELISA assay heparin-induced antibody formation is found in up to 50% of patients exposed to UFH. However, the serotonin release assay (SRA) which is believed to be more specific for HIT detects antibody formation in about 20% of patients. Five percent of patients receiving UFH develop thrombocytopenia (HIT) and half of these patients go on to develop heparin induced thrombocytopenia with thrombosis (HITT) which results in venous and arterial complications which can be life threatening, or result in loss of extremities.