title: Correlation of ELISA optical density with clinical diagnosis of heparin-induced thrombocytopenia: a retrospective study of 104 patients with positive anti-PF4/heparin ELISA.
abstract: BACKGROUND
  Enzyme-linked immunosorbent assay (ELISA) for antiplatelet factor 4 (anti-PF4)/heparin antibodies is expressed in terms of optical density (OD). Previous studies have shown correlation between OD and heparin-induced thrombocytopenia (HIT) diagnosis. However, these were mainly laboratory based.
  
  
  OBJECTIVE
  Retrospective correlation of clinical HIT to ELISA OD.
  
  
  METHODS
  We conducted a retrospective study involving 104 patients with a positive ELISA for anti-PF4/heparin antibodies between 2008 and May 2012. For each patient, a clinical diagnosis was adjudicated based on different features including "4T scores," laboratory results, and a 3-month clinical follow-up.
  
  
  RESULTS
  In this study, 28.8% of the patients were HIT positive, and 71.2% HIT negative. Patients with positive diagnosis had significantly higher mean OD (2.15 ± 0.76 vs 0.83 ± 0.62). Patients with OD <1.0 only had 3.4% positive diagnosis versus 45.5% for OD 1.0 to 2.0 and 78% for >2.0 units.
  
  
  CONCLUSIONS
  This study is a clinical confirmation that ELISA OD results are correlated with the probability of a clinical diagnosis of HIT.
authors.affiliation: 1Department of Hematology-Oncology, Centre hospitalier de l'Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Marc-André
authors.initials: MA
authors.lastname: Pearson
authors.forename: Chantal
authors.initials: C
authors.lastname: Nadeau
authors.forename: Normand
authors.initials: N
authors.lastname: Blais
mesh_terms: D000368:Aged; D001323:Autoantibodies / Q000032:analysis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006493:Heparin / Q000009:adverse effects / Q000276:immunology*; D006801:Humans; D008297:Male; D010978:Platelet Factor 4 / Q000276:immunology*; D012189:Retrospective Studies; D013921:Thrombocytopenia / Q000139:chemically induced / Q000175:diagnosis*
chemical_list: D001323:Autoantibodies; D010978:Platelet Factor 4; D006493:Heparin
keywords: ELISA; HIT; antiheparin antibody; diagnosis; optical density