Diagnosis of heparin-induced thrombocytopenia in the vascular surgery patient.
BACKGROUND
Recent studies have shown that patients with heparin-induced thrombocytopenia (HIT) form immunoglobulin G (IgG) and/or IgM antibodies directed against a complex of platelet factor 4 (PF4) and heparin. This recognition has resulted in the development of enzyme-linked immunosorbent assays (ELISAs) that use the heparin/PF4 complex as the antigen. 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 thrombotic disorders. All patients had the ELISA performed to detect IgG or IgM antibodies directed against heparin-PF4, as well as the 14C serotonin release assay, when HIT was clinically suspected.


RESULTS
HIT 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 returned to normal after heparin cessation. Only one of the four patients who tested positive by ELISA for IgG antibodies also tested positive by the 14C serotonin release assay. Treatment was significantly altered by the ELISA results in all five patients.


CONCLUSIONS
It is likely that the ELISA is more sensitive in the diagnosis of HIT than the more traditional aggregation tests, and it may emerge as a new gold standard. Prospective studies in which serial laboratory testing is combined with measurement of clinical outcomes are needed and will eventually provide a greater understanding of the full spectrum of HIT and the clinical settings that precipitate thrombosis in the vascular surgery patient.
Jackson
M R
MR
Department of Hematology and Vascular Biology, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA.
Krishnamurti
C
C
Aylesworth
C A
CA
Alving
B M
BM
D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005343:Fibrinolytic Agents / Q000009:adverse effects*; D006493:Heparin / Q000009:adverse effects* / Q000737:chemistry; D006494:Heparin Antagonists / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010976:Platelet Count; D010978:Platelet Factor 4 / Q000737:chemistry; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis; D014656:Vascular Surgical Procedures
D005343:Fibrinolytic Agents; D006494:Heparin Antagonists; D010978:Platelet Factor 4; D006493:Heparin