DIAGNOSIS OF HEPARIN-INDUCED THROMBOCYTOPENIA IN THE VASCULAR-SURGERYPATIENT

Background. Recent studies have shown that patients with heparin-induc ed thrombocytopenia (HIT) form immunoglobulin G (IgG) and/or IgM antib odies directed against a complex of platelet factor 4 (PF4) and hepari n. This recognition has resulted in the development of enzyme-linked i mmunosorbent assays (ELISAs) that use the heparin/PF4 complex as the a ntigen. This study describes the use of a standardized ELISA to assess antibody formation in five patients suspected of having HIT. Methods. Five patients received heparin for treatment of arterial or venous th rombotic disorders. All patients had the ELISA performed to detect IgG or IgM antibodies directed against heparin-PF4, as well as the C-14 s erotonin release assay, when HIT was clinically suspected. Results. HI T was diagnosed in four patients and ruled out in a fifth by using the ELISA. All patients had a 40% decrease in platelet count that returne d to normal after heparin cessation. Only one of the four patients who tested positive by ELISA for IgG antibodies also tested positive by t he C-14 serotonin release assay. Treatment wets significantly altered by the ELISA results in all five patients. Conclusions. It is likely t hat the ELISA is more sensitive in the diagnosis of HIT than the more traditional aggregation tests, and it may emerge as a new gold standar d. Prospective studies in which serial laboratory testing is combined with measurement of clinical outcomes are needed and will eventually p rovide a greater understanding of the full spectrum of HIT and the cli nical settings that precipitate thrombosis in the vascular surgery pat ient.