title: Evaluation of a flow cytometric assay for the confirmation of heparin-induced thrombocytopenia.
abstract: BACKGROUND
  Heparin-induced thrombocytopenia (HIT) is an immune-mediated thrombocytopenia associated with heparin therapy. The diagnosis consists of a combination of pretest probability and laboratory testing. The routinely available laboratory antigen binding assays for the detection of specific antibodies have a low HIT-positive predictive value; therefore, to exclude false-positive results, one of the functional assays should be performed. Functional assays evaluate the ability of heparin/PF4 antibodies to activate the platelets. The aim of our study was to validate the flow cytometric functional assay, based on the use of anti-CD61 and anti-CD62 antibodies, as a suitable diagnostic test for HIT.
  
  
  METHODS
  Sera from patients with a clinical suspicion of HIT were previously analyzed with screening IgG-specific ELISA, and 41 of those which were positive were selected for the functional assay.
  
  
  RESULTS
  Our results were compared to another functional assay - the HIPA (heparin-induced platelet aggregation assay). The diagnostic specificity of the flow cytometric assay was calculated based on HIPA results and was 83%.
  
  
  CONCLUSIONS
  Performing this functional test after the screening assay could significantly improve the specificity of HIT testing as heparin/PF4 antibodies are often not clinically significant.
authors.affiliation: Blood Transfusion Centre of Slovenia, Ljubljana, Slovenia.
authors.forename: E
authors.initials: E
authors.lastname: Maličev
authors.affiliation: University Medical Centre Ljubljana, Ljubljana, Slovenia.
authors.forename: M
authors.initials: M
authors.lastname: Kozak
authors.affiliation: Blood Transfusion Centre of Slovenia, Ljubljana, Slovenia.
authors.forename: P
authors.initials: P
authors.lastname: Rožman
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry / Q000379:methods* / Q000592:standards; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D010974:Platelet Aggregation; D013921:Thrombocytopenia / Q000097:blood* / Q000139:chemically induced*
chemical_list: D001323:Autoantibodies; D007074:Immunoglobulin G; D006493:Heparin
keywords: Heparin-induced thrombocytopenia; flow cytometry; functional assay; heparin-induced platelet aggregation assay; platelet activation