title: Prevalence of heparin/platelet factor 4 antibodies before and after cardiac surgery.
abstract: BACKGROUND
  The clinical significance of heparin/platelet factor 4 (PF4) antibodies in subjects undergoing cardiac surgery has not been systematically studied. We prospectively investigated whether the presence of heparin/PF4 antibodies would predict clinical thrombosis in this population.
  
  
  METHODS
  In 299 patients scheduled for cardiac surgery between October 2003 and March 2005, the heparin/PF4 antibodies and platelet count were measured immediately prior to, and 5 days after, surgery. The patients were followed up at 30 days for thrombotic complications.
  
  
  RESULTS
  The prevalence of the heparin/PF4 antibodies was 4.3% (13 of 299) prior to surgery and increased more than fivefold to 22.4% (62 of 277) postoperatively (p < 0.0001). Thromboembolic events occurred in 8.8% of patients with negative antibody and in 6.3% of patients with positive antibody (p = 0.77). Of the 62 patients with positive heparin/PF4 antibodies postoperatively, 22 (35.5%) were treated with a nonheparin anticoagulant. There was a trend toward higher rates of thromboembolic events in subjects who were thrombocytopenic compared with those who were not (17.1% and 6.7%, respectively, p = 0.06), regardless of antibody status. Two out of 8 patients (25%) with both thrombocytopenia and a positive antibody (clinical heparin-induced thrombocytopenia [HIT]) suffered a thromboembolic event, compared with 17 of 222 (7.7%) without clinical HIT (p = 0.13).
  
  
  CONCLUSIONS
  The high prevalence of antibodies to the heparin/PF4 complex after cardiac surgery and the low rate of thromboembolic complications in this population suggest that the antibody alone does not confer an increased risk of thrombotic complications. Monitoring for thrombocytopenia is recommended.
authors.affiliation: Department of Medicine, Cardiology Division, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
authors.forename: Brendan M
authors.initials: BM
authors.lastname: Everett
authors.forename: Robert
authors.initials: R
authors.lastname: Yeh
authors.forename: Shi Yin
authors.initials: SY
authors.lastname: Foo
authors.forename: David
authors.initials: D
authors.lastname: Criss
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Van Cott
authors.forename: Michael
authors.initials: M
authors.lastname: Laposata
authors.forename: Edwin G
authors.initials: EG
authors.lastname: Avery
authors.forename: William D
authors.initials: WD
authors.lastname: Hoffman
authors.forename: Jennifer
authors.initials: J
authors.lastname: Walker
authors.forename: David
authors.initials: D
authors.lastname: Torchiana
authors.forename: Ik-Kyung
authors.initials: IK
authors.lastname: Jang
mesh_terms: D000368:Aged; D000906:Antibodies / Q000097:blood*; D000925:Anticoagulants / Q000009:adverse effects / Q000276:immunology* / Q000627:therapeutic use; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D005260:Female; D006493:Heparin / Q000009:adverse effects / Q000276:immunology*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000276:immunology*; D011184:Postoperative Period; D011237:Predictive Value of Tests; D011300:Preoperative Care; D011446:Prospective Studies; D013921:Thrombocytopenia / Q000139:chemically induced; D013923:Thromboembolism / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control
chemical_list: D000906:Antibodies; D000925:Anticoagulants; D010978:Platelet Factor 4; D006493:Heparin