title: PF4/heparin antibody testing and treatment of heparin-induced thrombocytopenia in the intensive care unit.
abstract: BACKGROUND
  The diagnosis of heparin-induced thrombocytopenia (HIT) may be challenging in critically ill patients, as heparin exposures are ubiquitous, and thrombocytopenia is common. Unwarranted ordering and incorrect interpretation of heparin antibody tests can expose a patient to adverse drug events and imposes a significant economic burden on our health care system.
  
  
  METHODS
  A prospective, observational study was performed over 4 months on all adult patients located in 5 intensive care units, with a heparin antibody test ordered.
  
  
  RESULTS
  A platelet factor 4/heparin enzyme-linked immunosorbent assay (ELISA) test was ordered in 131 patients. In total, 110 patients had a low 4Ts score (0-3), and of these 103 had a negative ELISA result. In patients with a low 4Ts score, 0 (0%) of 110 had an optical density value >1.0. One hundred twenty-nine patients (98%) had another possible cause of thrombocytopenia identified.
  
  
  CONCLUSIONS
  In critically ill patients, low 4Ts scores indicate a low probability of HIT, and heparin antibody testing in these patients is not useful.
authors.affiliation: Department of Pharmacy, The Methodist Hospital, Houston, TX 77030, USA.mawanat@tmhs.org
authors.forename: Matthew
authors.initials: M
authors.lastname: Wanat
authors.forename: Kalliopi
authors.initials: K
authors.lastname: Fitousis
authors.forename: Jeff
authors.initials: J
authors.lastname: Hall
authors.forename: Lawrence
authors.initials: L
authors.lastname: Rice
mesh_terms: D000328:Adult; D000368:Aged; D000906:Antibodies / Q000097:blood*; D000925:Anticoagulants / Q000009:adverse effects*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006493:Heparin / Q000009:adverse effects* / Q000276:immunology; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000276:immunology*; D011446:Prospective Studies; D013921:Thrombocytopenia / Q000139:chemically induced*
chemical_list: D000906:Antibodies; D000925:Anticoagulants; D010978:Platelet Factor 4; D006493:Heparin