title: ABO blood type as a risk factor for secondary post-tonsillectomy haemorrhage.
abstract: BACKGROUND
  Blood type-O is associated with decreased expression of von Willebrand factor. Type-O patients suffer fewer thrombotic problems and may be more prone to haemorrhage. Secondary post-tonsillectomy haemorrhage is the most common severe complication of tonsillectomy. We propose that type-O blood may be over-represented in patients presenting with secondary bleeds.
  
  
  METHODS
  We reviewed patients treated in the Royal Victoria Eye and Ear Hospital and the Midwestern Regional Hospital for secondary post-tonsillectomy haemorrhages from 2001 to 2006.
  
  
  RESULTS
  Three-hundred and three patients suffered secondary post-tonsillectomy haemorrhages over the study period. Blood group data was available in 206 cases (68%). Sixty-three percent of patients studied were blood group O, compared with 55% of the general population (p=0.01).
  
  
  CONCLUSIONS
  Blood group O is disproportionately represented in secondary post-tonsillectomy haemorrhage patients. Although we cannot demonstrate causality, this association suggests that patients with type-O blood are more likely to suffer from secondary bleeds following tonsillectomy.
authors.affiliation: Department of Otolaryngology, Midwestern Regional Hospital, Dooradoyle, Limerick, Ireland. leonarddavid@eircom.net
authors.forename: David S
authors.initials: DS
authors.lastname: Leonard
authors.forename: John E
authors.initials: JE
authors.lastname: Fenton
authors.forename: Stephen
authors.initials: S
authors.lastname: Hone
mesh_terms: D000017:ABO Blood-Group System / Q000097:blood*; D006801:Humans; D019106:Postoperative Hemorrhage / Q000097:blood*; D012189:Retrospective Studies; D012307:Risk Factors; D014068:Tonsillectomy
chemical_list: D000017:ABO Blood-Group System