title: Thrombosis in suspected heparin-induced thrombocytopenia occurs more often with high antibody levels.
abstract: OBJECTIVE
  The study objective was to determine whether higher antiplatelet factor 4 (PF4)/heparin antibody levels using an enzyme-linked immunosorbent assay are associated with more frequent thrombotic events in patients with clinically suspected heparin-induced thrombocytopenia. Heparin-induced thrombocytopenia is an immune-mediated adverse drug reaction. An enzyme-linked immunosorbent assay detects anti-PF4/heparin antibodies to support a suspected clinical diagnosis of heparin-induced thrombocytopenia. The utility of quantitative enzyme-linked immunosorbent assay results is uncertain.
  
  
  METHODS
  Our single-centered study evaluated quantitative anti-PF4/heparin antibody levels using an enzyme-linked immunosorbent assay in consecutive hospitalized patients with a clinical suspicion of heparin-induced thrombocytopenia and positive anti-PF4/heparin antibody levels between July 2003 and December 2006.
  
  
  RESULTS
  Overall, anti-PF4/heparin antibody values were available for 318 patients with clinically suspected heparin-induced thrombocytopenia. The median level was 0.85 optical density units (range 0.31-4.0). The overall rate of arterial or venous thrombosis was 23.3%. A 1-unit increase in anti-PF4/heparin antibody level was associated with an approximate doubling in the odds of thrombosis by 30 days (odds ratio, 1.9; 95% confidence interval, 1.5-2.6; P=.0001). The proportion of patients with pulmonary embolism increased with higher anti-PF4/heparin antibody levels.
  
  
  CONCLUSIONS
  Higher levels of anti-PF4/heparin antibody are associated with increased thrombosis risk among patients with clinically suspected heparin-induced thrombocytopenia and might have clinical utility for prediction of true heparin-induced thrombocytopenia and the development of thrombosis.
authors.affiliation: Department of Pharmacy, Metrowest Medical Center, Framingham, MA, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Baroletti
authors.forename: Shelley
authors.initials: S
authors.lastname: Hurwitz
authors.forename: Nicole A S
authors.initials: NA
authors.lastname: Conti
authors.forename: John
authors.initials: J
authors.lastname: Fanikos
authors.forename: Gregory
authors.initials: G
authors.lastname: Piazza
authors.forename: Samuel Z
authors.initials: SZ
authors.lastname: Goldhaber
mesh_terms: D000368:Aged; D000906:Antibodies / Q000097:blood; D000925:Anticoagulants / Q000009:adverse effects*; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000276:immunology*; D013921:Thrombocytopenia / Q000139:chemically induced / Q000150:complications*; D013927:Thrombosis / Q000276:immunology*
chemical_list: D000906:Antibodies; D000925:Anticoagulants; D010978:Platelet Factor 4; D006493:Heparin