title: Overdiagnosis of heparin-induced thrombocytopenia in surgical ICU patients.
abstract: BACKGROUND
  Heparin use in surgical patients places them at increased risk for developing heparin-induced thrombocytopenia (HIT). The false positive rate of HIT using the current standard criteria is unknown in surgical ICU patients, who often have confounding factors that cause thrombocytopenia.
  
  
  METHODS
  Surgical ICU patients, admitted over a 2-year period with a positive screening test for HIT (platelet factor [PF] 4 ≥ 0.4 optical density [OD]), were reviewed retrospectively at a single institution. Correlation of the Warkentin 4-T score and commercial heparin PF4 ELISA with serotonin releasing assay (SRA) was performed. Logistic regression was used to determine independent risk factors associated with the development of HIT.
  
  
  RESULTS
  PF4 tests were requested in 643 patients based on a clinical suspicion of HIT. Of these, 104 patients had a PF4 result, an SRA value (%), and a 4-T score available. Twenty patients (19%) had true positive HIT, defined as a positive PF4 and positive SRA (SRA ≥ 20%). Eighty-four patients (81%) were false positive, defined as a positive PF4 and negative SRA. Five of 58 patients with Warkentin score of 0 to 3, and 6 of 14 patients with Warkentin score of 6 to 8 were HIT positive by SRA.
  
  
  CONCLUSIONS
  In surgical ICU patients, clinical suspicion for HIT necessitates PF4 and SRA analysis. Testing for HIT or treatment with a direct thrombin inhibitor should not depend on the Warkentin 4-T score alone. Although a PF4 ≥ 0.4 OD is considered a positive screening test for HIT, a PF4 ≥ 2.0 OD is preferable in surgical ICU patients.
authors.affiliation: Department of Surgery, Division of Trauma and Surgical Critical Care, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
authors.forename: Cherisse
authors.initials: C
authors.lastname: Berry
authors.forename: Oxana
authors.initials: O
authors.lastname: Tcherniantchouk
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Ley
authors.forename: Ali
authors.initials: A
authors.lastname: Salim
authors.forename: James
authors.initials: J
authors.lastname: Mirocha
authors.forename: Sylvia
authors.initials: S
authors.lastname: Martin-Stone
authors.forename: Dennis
authors.initials: D
authors.lastname: Stolpner
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Margulies
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000009:adverse effects*; D003422:Critical Care; D003951:Diagnostic Errors; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010976:Platelet Count; D010978:Platelet Factor 4 / Q000097:blood; D011183:Postoperative Complications; D012189:Retrospective Studies; D012307:Risk Factors; D013921:Thrombocytopenia / Q000097:blood / Q000139:chemically induced* / Q000175:diagnosis*; D013997:Time Factors
chemical_list: D000925:Anticoagulants; D010978:Platelet Factor 4; D006493:Heparin