title: The pre-operative levels of haemoglobin in the blood can be used to predict the risk of allogenic blood transfusion after total knee arthroplasty.
abstract: OBJECTIVE
  The pre-operative level of haemoglobin is the strongest predictor of the peri-operative requirement for blood transfusion after total knee arthroplasty (TKA). There are, however, no studies reporting a value that could be considered to be appropriate pre-operatively. This study aimed to identify threshold pre-operative levels of haemoglobin that would predict the requirement for blood transfusion in patients who undergo TKA.
  
  
  METHODS
  Analysis of receiver operator characteristic (ROC) curves of 2284 consecutive patients undergoing unilateral TKA was used to determine gender specific thresholds predicting peri-operative transfusion with the highest combined sensitivity and specificity (area under ROC curve 0.79 for males; 0.78 for females).
  
  
  RESULTS
  Threshold levels of 13.75 g/dl for males and 12.75 g/dl for females were identified. The rates of transfusion in males and females, respectively above these levels were 3.37% and 7.11%, while below these levels, they were 16.13% and 28.17%. Pre-operative anaemia increased the rate of transfusion by 6.38 times in males and 6.27 times in females. Blood transfusion was associated with an increased incidence of early post-operative confusion (odds ratio (OR) = 3.44), cardiac arrhythmia (OR = 5.90), urinary catheterisation (OR = 1.60), the incidence of deep infection (OR = 4.03) and mortality (OR = 2.35) one year post-operatively, and increased length of stay (eight days vs six days, p < 0.001).
  
  
  CONCLUSIONS
  Uncorrected low pre-operative levels of haemoglobin put patients at potentially modifiable risk and attempts should be made to correct this before TKA. Target thresholds for the levels of haemoglobin pre-operatively in males and females are proposed.
  
  
  CONCLUSIONS
  Low pre-operative haemoglobin levels put patients at unnecessary risk and should be corrected prior to surgery.
authors.affiliation: Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh EH16 4SA, UK.
authors.forename: J F
authors.initials: JF
authors.lastname: Maempel
authors.affiliation: Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh EH16 4SA, UK.
authors.forename: N R
authors.initials: NR
authors.lastname: Wickramasinghe
authors.affiliation: Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh EH16 4SA, UK.
authors.forename: N D
authors.initials: ND
authors.lastname: Clement
authors.affiliation: Victoria Hospital, Hayfield Road, Kirkcaldy KY2 5AH, UK.
authors.forename: I J
authors.initials: IJ
authors.lastname: Brenkel
authors.affiliation: Victoria Hospital, Hayfield Road, Kirkcaldy KY2 5AH, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Walmsley
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001804:Blood Transfusion, Autologous / Q000706:statistics & numerical data*; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011183:Postoperative Complications / Q000097:blood / Q000453:epidemiology*; D011184:Postoperative Period; D011237:Predictive Value of Tests; D057234:Preoperative Period; D012372:ROC Curve; D012189:Retrospective Studies; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D006454:Hemoglobins
keywords: total knee arthroplasty; allogenic blood transfusion; pre-operative haemoglobin concentration