Core Outcome Measures in Effectiveness Trials

COMET Initiative


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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 1087 references of planned, ongoing and completed work.

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

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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

  • Wednesday 31 October, 2018 - New podcast out now

    Hans-Georg Eichler (Senior Medial Officer, European Medicines Agency) shares why he thinks core outcome sets are taking on a new importance. Watch the podcast in full now. 

  • Thursday 10 May, 2018 - Prof Paula Williamson elected to join the prestigious Fellowship of the Academy of Medical Sciences

    48 of the UK’s world leading researchers have been elected to join the prestigious Fellowship of the Academy of Medical Sciences, it has been announced today (Thursday 10 May).

    The new Fellows have been elected for their outstanding contributions to biomedical and health science, leading research discoveries, and translating developments into benefits for patients and the wider society.

    This year's elected Fellows have expertise that spans sleep research, infectious and tropical diseases, diabetes medicine, parasite biology and ultrasound research and technology among many other fields.

    Professor Paula Williamson, the chair of the COMET Management Group, is among those to be elected. Congratulations Paula, truly deserved.

    Read the full announcement 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

Recently Added Studies

  • Harmonization of Outcome Parameters and Evaluation (HOPE) for actinic keratosis: Development of a core outcome from a German-European perspective

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  • A systematic review of outcome and outcome-measure reporting in randomised trials evaluating surgical interventions for anterior-compartment vaginal prolapse: a call to action to develop a core outcome set

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  • Development of a Core Outcome Set (COS) for Thumb Trapeziometacarpal Osteoarthritis

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  • Development of Core Outcomes Measures for Clinical Trials in Primary Sclerosing Cholangitis (PSC)

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  • Reporting of outcomes in gastric cancer surgery trials: a systematic review

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