title: Validity of the 6 min walk test in prediction of the anaerobic threshold before major non-cardiac surgery.
abstract: BACKGROUND
  For perioperative risk stratification, a robust, practical test could be used where cardiopulmonary exercise testing (CPET) is unavailable. The aim of this study was to assess the utility of the 6 min walk test (6MWT) distance to discriminate between low and high anaerobic threshold (AT) in patients awaiting major non-cardiac surgery.
  
  
  METHODS
  In 110 participants, we obtained oxygen consumption at the AT from CPET and recorded the distance walked (in m) during a 6MWT. Receiver operating characteristic (ROC) curve analysis was used to derive two different cut-points for 6MWT distance in predicting an AT of <11 ml O(2) kg(-1) min(-1); one using the highest sum of sensitivity and specificity (conventional method) and the other adopting a 2:1 weighting in favour of sensitivity. In addition, using a novel linear regression-based technique, we obtained lower and upper cut-points for 6MWT distance that are predictive of an AT that is likely to be (P≥0.75) <11 or >11 ml O(2) kg(-1) min(-1).
  
  
  RESULTS
  The ROC curve analysis revealed an area under the curve of 0.85 (95% confidence interval, 0.77-0.91). The optimum cut-points were <440 m (conventional method) and <502 m (sensitivity-weighted approach). The regression-based lower and upper 6MWT distance cut-points were <427 and >563 m, respectively.
  
  
  CONCLUSIONS
  Patients walking >563 m in the 6MWT do not routinely require CPET; those walking <427 m should be referred for further evaluation. In situations of 'clinical uncertainty' (≥427 but ≤563 m), the number of clinical risk factors and magnitude of surgery should be incorporated into the decision-making process. The 6MWT is a useful clinical tool to screen and risk stratify patients in departments where CPET is unavailable.
authors: Department of Anaesthesia, The James Cook University Hospital, Middlesbrough, UK. rhona.sinclair@ncl.ac.uk
authors: R C F
authors: RC
authors: Sinclair
authors: A M
authors: AM
authors: Batterham
authors: S
authors: S
authors: Davies
authors: L
authors: L
authors: Cawthorn
authors: G R
authors: GR
authors: Danjoux
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015308:Anaerobic Threshold; D019540:Area Under Curve; D002245:Carbon Dioxide / Q000097:blood; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D011237:Predictive Value of Tests; D011300:Preoperative Care; D012372:ROC Curve; D012044:Regression Analysis; D015203:Reproducibility of Results; D013514:Surgical Procedures, Operative / Q000379:methods*; D016138:Walking / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide