title: The epidemiology of red cell transfusion.
abstract: OBJECTIVE
  Understanding of the clinical usage of red cells is limited despite its importance in transfusion practice improvement and planning for blood supply requirements. Previous studies have described red cell use based upon ICD and hospital discharge codes; however, such approaches are open to misclassification. This study addresses this limitation by undertaking an epidemiological analysis of red cell use using case note review.
  
  
  METHODS
  Patient, disease and contextual factors were extracted from the medical records of a randomly selected sample of hospital patients in Northern Ireland who received a red cell transfusion during 2005 (n=1474).
  
  
  RESULTS
  Transfused patients received a total of 3804 units (median of two units per transfusion episode). Most transfusions occurred in a medical setting (71%). Patients undergoing treatment for gastrointestinal conditions were responsible for the majority of the demand (29% of transfusion episodes; 34% of red cell units). The presence of bleeding and abnormal tests of coagulation were associated with receiving larger transfusions (≥ 3 units), while patients undergoing orthopaedic surgery and those with a haemoglobin level over 7 g/dl had the lowest risk of receiving ≥ 3 units in any one transfusion episode.
  
  
  CONCLUSIONS
  The majority of red cells are now prescribed in a medical setting. With an ageing population and increasing therapeutic interventions, the demand for blood is likely to increase despite efforts to reduce usage by eliminating inappropriate transfusions through education and behaviour change. The post-transfusion target (and therefore the number of units to transfuse) for any given clinical situation as well as guidance on a 'safe' transfusion threshold should be considered in future guidelines.
authors.affiliation: Centre for Excellence in Public Health, Queens University Belfast, Belfast, UK. p.barr@qub.ac.uk
authors.forename: P J
authors.initials: PJ
authors.lastname: Barr
authors.forename: M
authors.initials: M
authors.lastname: Donnelly
authors.forename: K
authors.initials: K
authors.lastname: Morris
authors.forename: M
authors.initials: M
authors.lastname: Parker
authors.forename: C
authors.initials: C
authors.lastname: Cardwell
authors.forename: K E M
authors.initials: KE
authors.lastname: Bailie
mesh_terms: D001780:Blood Coagulation Tests; D017707:Erythrocyte Transfusion; D006470:Hemorrhage / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D017410:Practice Guidelines as Topic; D012189:Retrospective Studies; D012307:Risk Factors