A Core Outcome Set for the Benefits and Adverse Events of Bariatric and Metabolic Surgery: The BARIACT Project


Bariatric and metabolic surgery is used as a treatment for patients with severe and complex obesity. However, there is a need to improve outcome selection and reporting in bariatric surgery trials. A Core Outcome Set (COS), an agreed minimum set of outcomes reported in all studies of a specific condition, may achieve this. Here, we present the development of a COS for BARIAtric and metabolic surgery Clinical Trials—the BARIACT Study.

Methods and Findings

Outcomes identified from systematic reviews and patient interviews informed a questionnaire survey. Patients and health professionals were surveyed three times and asked to rate the importance of each item on a 1–9 scale. Delphi methods provided anonymised feedback to participants. Items not meeting predefined criteria were discarded between rounds. Remaining items were discussed at consensus meetings, held separately with patients and professionals, where the COS was agreed. Data sources identified 2,990 outcomes, which were used to develop a 130-item questionnaire. Round 1 response rates were moderate but subsequently improved to above 75% for other rounds. After rounds 2 and 3, 81 and 14 items were discarded, respectively, leaving 35 items for discussion at consensus meetings. The final COS included nine items: “weight,” “diabetes status,” “cardiovascular risk,” “overall quality of life (QOL),” “mortality,” “technical complications of the specific operation,” “any re-operation/re-intervention,” “dysphagia/regurgitation,” and “micronutrient status.” The main limitation of this study was that it was based in the United Kingdom only.


The COS is recommended to be used as a minimum in all trials of bariatric and metabolic surgery. Adoption of the COS will improve data synthesis and the value of research data. Future work will establish methods for the measurement of the outcomes in the COS.


The development of a COS for BARIAtric and metabolic surgery Clinical Trials


Karen D. Coulman,
James Hopkins,
Sara T. Brookes,
Katy Chalmers,
Barry Main,
Amanda Owen-Smith,
Robert C. Andrews,
James Byrne,
Jenny L. Donovan,
Graziella Mazza,
Barnaby C. Reeves,
Chris A. Rogers,
Janice L. Thompson,
Richard Welbourn,
Sarah Wordsworth,
Jane M. Blazeby,
BARIACT working group


Journal: PLOS Medicine
Pages: -
Year: 2016

Further Study Information

Current Stage: Completed
Date: October 2011 - August 2015
Funding source(s): HTA Clinical Trials and Evaluation Board (BY-BAND trial)

Health Area

Disease Category: Endocrine & metabolic

Disease Name: Obesity

Target Population

Age Range: 16 - 100

Sex: Either

Nature of Intervention: Surgery

Stakeholders Involved

- Clinical experts
- Consumers (patients)

Study Type

- COS for clinical trials or clinical research
- Patient perspectives
- Systematic review of outcomes measured in trials
- Systematic review of qualitative research


- Consensus meeting
- Delphi process
- Systematic review
- Interview
- Survey

Three stages of work will be undertaken
i) systematic reviews of the clinical outcomes in reported trial literature for bariatric surgery to identify comprehensive list of potential clinical outcomes, using the 2009 HTA review and an up-to-date literature search from 2008-2011.

ii) This will be used to produce a questionnaire which will be sent to survey approximately 200 key stakeholders (clinicians, and allied health professionals) using at least 2 rounds of the Delphi methodology to refine the core outcomes

iii) consensus meetings with key stakeholders to consider the processes, results and potential core outcomes.

Will involve:
Bariatric Surgeons
Bariatric Clinical Nurse Specialists
Bariatric Dieticians
Bariatric Physicians and Endocrinologists
Anaesthetists with an interest in bariatric surgery