Core Outcome Measures in Effectiveness Trials

COMET Initiative

The COMET (Core Outcome Measures in Effectiveness Trials) Initiative brings together people interested in the development and application of agreed standardised sets of outcomes, known as ‘core outcome sets’ (COS). These sets represent the minimum that should be measured and reported in all clinical trials of a specific condition, and are also suitable for use in clinical audit or research other than randomised trials. The existence or use of a core outcome set does not imply that outcomes in a particular trial should be restricted to those in the relevant core outcome set. Rather, there is an expectation that the core outcomes will be collected and reported, making it easier for the results of trials to be compared, contrasted and combined as appropriate; while researchers continue to explore other outcomes as well. COMET aims to collate and stimulate relevant resources, both applied and methodological, to facilitate exchange of ideas and information, and to foster methodological research in this area. The COMET Handbook Version 1.0 is available here.

When searching the COMET database, please note that a systematic review is currently underway to identify eligible material, and we are continually updating the database as we identify eligible studies. Therefore, the records retrieved by any search might increase on a daily basis.


The COMET database currently contains 1017 references of planned, ongoing and completed work.

The keyword used for the search will be compared with study title, abstract and author's surname.

View full search options

To view a demonstration of how to search the COMET database click here

Core resource pack


Useful references for core outcome set developers.

This includes an overview of the problems with outcomes in trials, key issues to consider in the development of a core outcome set, examples of core outcome set development, and things to think about once a COS is agreed. To read more, click here.

Latest News

  • Thursday 12 April, 2018 - New: Podcasts

    The first edition in a new collection of Podcasts comes from Hywel Williams, Director of the NIHR Health Technology Assessment Programme, Professor of Dermato-Epidemiology and Co-Director of the Centre of Evidence-Based Dermatology.

    Hywel explains why he thinks that " the development and use of core outcome sets is one of the most important advances to date in evidence-based medicine and surgery."

    Watch the Podcast, in full, here.

  • Monday 26 March, 2018 - Do you have a consensus meeting planned or coming up?

    If you are planning an upcoming consensus meeting and would be happy for an early career researcher to observe the meeting in order to learn from the experience, please let us know.  This would be an invaluable opportunity to gain experience in the development of core outcome sets for potential COS developers. Please email info@comet-initiative.org

  • Tuesday 13 March, 2018 - Exploring patient and public experience of involvement in the design of COS studies

    Lucy, a PhD student at the University of Liverpool, is interviewing patients and members of the public who have inputted or advised on the design, planning and/or running of a COS study.

    If your COS study is completed or close to completion, could you help Lucy access interviewees? If so, please get in touch with Lucy by emailing Lbrading@liverpool.ac.uk or giving her a call on +44 (0)151 794 9964.

    Many thanks in advance.

Recently Added Studies

  • Development of a core outcome set for diabetic foot ulceration

    [View details]
  • Development of a Core set of Outcome Measures for the Thumb Carpometacarpal Osteoarthritis

    [View details]
  • Defining core outcomes for school-based intervention studies on preventing childhood overweight and obesity

    [View details]
  • Patients' opinions on outcomes following critical illness

    [View details]
  • Bladder Cancer Core Outcome Sets (B-COS) programme encompassing 1) non-muscle-invasive bladder cancer 2) muscle invasive bladder cancer and 3) metastatic bladder cancer

    [View details]

Subscribe to our mailing list

* indicates required

The site uses cookies, some may have been set already. Please refer to our privacy policy & cookie usage statement.
If you continue to use the site we'll assume you're happy to accept the cookies.