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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Date data sharing statement initially provided
Date results information initially provided
Type of registration
Prospectively registered

Titles & IDs
Public title
Use of the six minute walk test to predict recovery and complications in morbidly obese patients undergoing elective surgery
Scientific title
In severely obese patients presenting for elective surgery, can the six minute walk test predict recovery and medical complications?
Secondary ID [1] 287886 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Severe obesity 296771 0
Post-operative functional recovery and medical complications 296772 0
Condition category
Condition code
Diet and Nutrition 297006 297006 0 0
Surgery 297017 297017 0 0
Other surgery

Study type
Description of intervention(s) / exposure
Performance of the six minute walk test. This measures the distance that a patient can walk in 6 minutes and is follows steps delineated by a standard operating procedure. This will occur in the pre-operative assessment clinic and be supervised by a research assistant who will be trained in supervision of the test..
Performance of spirometry, measurement of waist and hip circumferences, and of serum NT pro-BNP will also occur in the pre-operative assessment clinic. These are study measures and are not measured routinely.
Patients visit the pre-operative assessment clinics between one day and 6 weeks prior to their scheduled date of surgery.
Intervention code [1] 293252 0
Early detection / Screening
Comparator / control treatment
No control group
Control group

Primary outcome [1] 296602 0
Functional recovery as measured by the WHODAS 2.0 and QOR-15 tools.
Timepoint [1] 296602 0
The recovery measurement surveys will occur at the following times after surgery: QOR-15 at 3 and 30 days, WHODAS 2.0 at 30 days and at 6 months.
Secondary outcome [1] 318892 0
Medical complications will be measured using a standard checklist with standard measures and definitions. Data will be gathered by a research assistant searching the medical record, and confirming with the patient at the 30 day post-operative interview.
Timepoint [1] 318892 0
Within first 30 days post-operatively.

Key inclusion criteria
Age => 18 years
BMI => 35 at pre-admission clinic
Booked for elective non-cardiac surgery at Wollongong hospital
Minimum age
18 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Inadequate time to complete the 6MWT pre-operatively
Presence of medical contra-indications to the 6MWT test as per American Thoracic Society guidelines

Study design
Purpose of the study
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?

Intervention assignment
Single group
Other design features
Follow-up to 6 months post-operatively
The aim of this trial is to test the predictive value of a pre-operative screening tool for risk assessment and stratification in a specific patient population group.
Not Applicable
Type of endpoint(s)
Statistical methods / analysis
Correlation statistics: mainly receiver operating characteristic (ROC) method, with linear regression and use of t-tests where appropriate. Sample size was determined using published tables. We estimated the correlation co-efficient to be 0.5 as the outcomes are somewhat nut not completely correlated. We chose confidence intervals to be no wider than -/+ 0.1. A sample size of 219 met these requirements. We added c 10% extra to this to account for losses between study recruitment and completion to give an overall sample size of 250. Based on an audit of numbers of severely obese patients presenting to the Wollongong pre-operative clinic, we estimated that up to 18 months should be sufficient to recruit this sample size.

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 4629 0
Wollongong Hospital - Wollongong
Recruitment postcode(s) [1] 12219 0
2500 - Wollongong

Funding & Sponsors
Funding source category [1] 292382 0
Name [1] 292382 0
ANZCA (Australia and New Zealand College of Anaesthetists) Research Committee
Address [1] 292382 0
630 St Kilda Rd
Vic 3004
Country [1] 292382 0
Funding source category [2] 306628 0
Name [2] 306628 0
Illawarra Health and Medical Research Institute: University of Wollongong
Address [2] 306628 0
University of Wollongong
Northfields Ave, North Wollongong
NSW 2500
Country [2] 306628 0
Primary sponsor type
Natalie Smith
c/- Department of Anaesthesia
Wollongong Hospital
Crown St, Wollongong
NSW 2500
Secondary sponsor category [1] 291071 0
Name [1] 291071 0
Address [1] 291071 0
Country [1] 291071 0

Ethics approval
Ethics application status
Ethics committee name [1] 293852 0
UOW and ISLHD Health and Medical Research Ethics Committee
Ethics committee address [1] 293852 0
Ethics Unit, Research Services Office
University of Wollongong
Northfields Ave, Wollongong
NSW 2522
Ethics committee country [1] 293852 0
Date submitted for ethics approval [1] 293852 0
Approval date [1] 293852 0
Ethics approval number [1] 293852 0
Ethics number HE15/379

Brief summary
Wollongong Hospital is a large regional hospital that performs approximately 13 000 episodes of operative care per year. The range of surgery performed covers all areas apart from cardio-thoracic, including neurosurgery, vascular, orthopaedics, urology, ENT general, colo-rectal, endoscopy, imaging, obstetrics and gynaecology, general paediatrics, and plastic surgery. The anaesthesia department at Wollongong Hospital has an audit and research focus particularly in the fields of education, obesity, and geriatric care.

Australian Bureau of Statistics data report that 62.8% of adult Australians were overweight or obese in 2011-12. Of this number, approximately 12% had a body mass index (BMI) greater than or equal to 35, which, in the presence of comorbidities, has been defined as morbid obesity. Local data show that at least 13% of patients undergoing elective surgery at Wollongong Hospital each year are morbidly obese. Most of the literature suggests that morbidly obese patients have higher rates of clinical complications in the post-operative period than the non-obese although this finding has not been universally reported. Assessment of risk in obese patients cannot accurately be based on the presence of obesity alone.

Measurement of functional capacity pre-operatively is considered essential for useful risk stratification and prediction of post-operative outcomes. Cardiopulmonary exercise testing (CPET) is the gold standard for assessing cardio-respiratory fitness. However, CPET is expensive, resource-intensive, and requires a dedicated specialist laboratory and trained technicians. In contrast, the six minute walk test (6MWT) is a simple and cheap test for evaluation of cardio-respiratory function that has compared well to CPEX in previous studies. It may be ideal for assessing functional capacity in morbidly obese patients as it can be performed by existing staff in a pre-operative assessment area and has been shown to be safe for morbidly obese patients in multiple papers. There are currently no published data on the use of the 6MWT as a screening tool to predict high risk in obese patients undergoing surgery.

The aim of this study is to assess the ability of the 6MWT to predict postoperative functional recovery and medical complications in morbidly obese patients in Wollongong Hospital who attend a pre-admission assessment clinic (PAC). Identification of this subset of patients would allow peri-operative teams to target further investigations, optimise surgical planning, and stratify the intensity of intra-operative and post-operative care. With these strategies, it may be possible to decrease morbidity and mortality and the associated healthcare costs to the community.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 61522 0
A/Prof Natalie Smith
Address 61522 0
c/- Department of Anaesthesia
Wollongong Hospital
Crown St, Wollongong, NSW 2500
Country 61522 0
Phone 61522 0
+61 2 4255 1560
Fax 61522 0
Email 61522 0
Contact person for public queries
Name 61523 0
A/Prof Natalie Smith
Address 61523 0
c/- Department of Anaesthesia
Wollongong Hospital
Crown St, Wollongong, NSW 2500
Country 61523 0
Phone 61523 0
+61 2 4255 1560
Fax 61523 0
Email 61523 0
Contact person for scientific queries
Name 61524 0
A/Prof Natalie Smith
Address 61524 0
c/- Department of Anaesthesia
Wollongong Hospital
Crown St, Wollongong, NSW 2500
Country 61524 0
Phone 61524 0
+61 2 4255 1560
Fax 61524 0
Email 61524 0

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
What data in particular will be shared?
De-idientified individual participant data after publication
When will data be available (start and end dates)?
Start date: After publication
End date: no end date determined
Available to whom?
Researchers who provide a sound proposal at the discretion of the chief investigator
Available for what types of analyses?
To achieve aims in a proposal, for meta-analysis
How or where can data be obtained?
By contacting the chief investigator by email:
What supporting documents are/will be available?
Study protocol
Statistical analysis plan
Informed consent form
Clinical study report
Ethical approval
How or where can supporting documents be obtained?
Type [1] 9014 0
Study protocol
Citation [1] 9014 0
Link [1] 9014 0
Email [1] 9014 0
Other [1] 9014 0
The protocol will be available as part of the main publication of results
Attachment [1] 9014 0
Type [2] 9015 0
Statistical analysis plan
Citation [2] 9015 0
Link [2] 9015 0
Email [2] 9015 0
Other [2] 9015 0
Attachment [2] 9015 0
Type [3] 9016 0
Informed consent form
Citation [3] 9016 0
Link [3] 9016 0
Email [3] 9016 0
Other [3] 9016 0
Attachment [3] 9016 0
Type [4] 9017 0
Clinical study report
Citation [4] 9017 0
Link [4] 9017 0
Email [4] 9017 0
Other [4] 9017 0
Attachment [4] 9017 0
Type [5] 9018 0
Ethical approval
Citation [5] 9018 0
Link [5] 9018 0
Email [5] 9018 0
Other [5] 9018 0
Attachment [5] 9018 0
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary