title: Preoperative haemoglobin cut-off values for the prediction of post-operative transfusion in total knee arthroplasty.
abstract: OBJECTIVE
  The purpose of this study is to determine preoperative haemoglobin cut-off values that could accurately predict post-operative transfusion outcome in patients undergoing primary unilateral total knee arthroplasty (TKA). This will allow surgeons to provide selective preoperative type and screen to only patients at high risk of transfusion.
  
  
  METHODS
  A total of 1457 patients diagnosed with osteoarthritis and underwent primary unilateral TKA between January 2012 and December 2014 were retrospectively reviewed. Logistic regression analyses were applied to identify factors that could predict transfusion outcome.
  
  
  RESULTS
  A total of 37 patients (2.5 %) were transfused postoperatively. Univariate analysis revealed preoperative haemoglobin (p < 0.001), age (p < 0.001), preoperative haematocrit (p < 0.001), and preoperative creatinine (p < 0.001) to be significant predictors. In the multivariate analysis with patients dichotomised at 70 years of age, preoperative haemoglobin remained significant with adjusted odds ratio of 0.33. Receiver operating characteristic curve identified the preoperative haemoglobin cut-off values to be 12.4 g/dL (AUC = 0.86, sensitivity = 87.5 %, specificity = 77.2 %) and 12.1 g/dL (AUC = 0.85, sensitivity = 69.2 %, specificity = 87.1 %) for age above and below 70, respectively.
  
  
  CONCLUSIONS
  The authors recommend preoperative haemoglobin cut-off values of 12.4 g/dL for age above 70 and 12.1 g/dL for age below 70 to be used to predict post-operative transfusion requirements in TKA. To maximise the utilisation of blood resources, the authors recommend that only patients with haemoglobin level below the cut-off should receive routine preoperative type and screen before TKA.
  
  
  METHODS
  IV.
authors.affiliation: Duke-NUS Medical School, 8 College Road, Singapore, 169857, Singapore. jared.yeh.zy@gmail.com.
authors.forename: Jared Ze Yang
authors.initials: JZ
authors.lastname: Yeh
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Jerry Yongqiang
authors.initials: JY
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Hamid Rahmatullah
authors.initials: HR
authors.lastname: Bin Abd Razak
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Bryan Huai Gu
authors.initials: BH
authors.lastname: Loh
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Ying
authors.initials: Y
authors.lastname: Hao
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Andy Khye Soon
authors.initials: AK
authors.lastname: Yew
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Shi-Lu
authors.initials: SL
authors.lastname: Chia
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Ngai Nung
authors.initials: NN
authors.lastname: Lo
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, Singapore, 169608, Singapore.
authors.forename: Seng Jin
authors.initials: SJ
authors.lastname: Yeo
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D016063:Blood Loss, Surgical; D001803:Blood Transfusion; D003404:Creatinine / Q000097:blood; D005260:Female; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D020370:Osteoarthritis, Knee / Q000601:surgery; D011182:Postoperative Care; D012372:ROC Curve; D012189:Retrospective Studies
chemical_list: D006454:Hemoglobins; D003404:Creatinine
keywords: Haemoglobin; Knee replacement; Preoperative; Total knee arthroplasty; Transfusion