title: Measurement of Exercise Tolerance before Surgery (METS) study: a protocol for an international multicentre prospective cohort study of cardiopulmonary exercise testing prior to major non-cardiac surgery.
abstract: BACKGROUND
  Preoperative functional capacity is considered an important risk factor for cardiovascular and other complications of major non-cardiac surgery. Nonetheless, the usual approach for estimating preoperative functional capacity, namely doctors' subjective assessment, may not accurately predict postoperative morbidity or mortality. 3 possible alternatives are cardiopulmonary exercise testing; the Duke Activity Status Index, a standardised questionnaire for estimating functional capacity; and the serum concentration of N-terminal pro-B-type natriuretic peptide (NT pro-BNP), a biomarker for heart failure and cardiac ischaemia.
  
  
  METHODS
  The Measurement of Exercise Tolerance before Surgery (METS) Study is a multicentre prospective cohort study of patients undergoing major elective non-cardiac surgery at 25 participating study sites in Australia, Canada, New Zealand and the UK. We aim to recruit 1723 participants. Prior to surgery, participants undergo symptom-limited cardiopulmonary exercise testing on a cycle ergometer, complete the Duke Activity Status Index questionnaire, undergo blood sampling to measure serum NT pro-BNP concentration and have their functional capacity subjectively assessed by their responsible doctors. Participants are followed for 1 year after surgery to assess vital status, postoperative complications and general health utilities. The primary outcome is all-cause death or non-fatal myocardial infarction within 30 days after surgery, and the secondary outcome is all-cause death within 1 year after surgery. Both receiver-operating-characteristic curve methods and risk reclassification table methods will be used to compare the prognostic accuracy of preoperative subjective assessment, peak oxygen consumption during cardiopulmonary exercise testing, Duke Activity Status Index scores and serum NT pro-BNP concentration.
  
  
  BACKGROUND
  The METS Study has received research ethics board approval at all sites. Participant recruitment began in March 2013, and 1-year follow-up is expected to finish in 2016. Publication of the results of the METS Study is anticipated to occur in 2017.
authors.affiliation: St. Michael's Hospital/Toronto General Hospital/University of Toronto, Toronto, Ontario, Canada.
authors.forename: Duminda N
authors.identifier: http://orcid.org/0000-0002-5897-8605
authors.initials: DN
authors.lastname: Wijeysundera
authors.affiliation: Queen Mary University of London, London, UK.
authors.forename: Rupert M
authors.initials: RM
authors.lastname: Pearse
authors.affiliation: Alfred Hospital/Monash University, Melbourne, Victoria, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Shulman
authors.affiliation: Queen Mary University of London, London, UK.
authors.forename: Tom E F
authors.initials: TE
authors.lastname: Abbott
authors.affiliation: St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Torres
authors.affiliation: NHS Grampian, Aberdeen, UK.
authors.forename: Bernard L
authors.initials: BL
authors.lastname: Croal
authors.affiliation: University Health Network/Mount Sinai Hospital/University of Toronto, Toronto, Ontario, Canada.
authors.forename: John T
authors.initials: JT
authors.lastname: Granton
authors.affiliation: University of Toronto/St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Thorpe
authors.affiliation: University Hospital Southampton/University of Southampton, Southampton, UK.
authors.forename: Michael P W
authors.initials: MP
authors.lastname: Grocott
authors.affiliation: Alfred Hospital/Monash University, Melbourne, Victoria, Australia.
authors.forename: Catherine
authors.initials: C
authors.lastname: Farrington
authors.affiliation: Alfred Hospital/Monash University, Melbourne, Victoria, Australia.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Myles
authors.affiliation: Sunnybrook Health Sciences Centre/University of Toronto, Toronto, Ontario, Canada.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Cuthbertson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D015415:Biomarkers / Q000097:blood; D002170:Canada; D017558:Elective Surgical Procedures / Q000401:mortality*; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D009203:Myocardial Infarction / Q000453:epidemiology*; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D009520:New Zealand; D010446:Peptide Fragments / Q000097:blood*; D011184:Postoperative Period; D057234:Preoperative Period; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012107:Research Design; D012307:Risk Factors; D006113:United Kingdom
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain
keywords: Cardiopulmonary exercise testing; Natriuretic peptides; Postoperative complications; Preoperative assessment; Risk prediction