Core Outcome Measures in Effectiveness Trials

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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’. 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.

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 596 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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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 29 January, 2015 - A core set of trial outcomes for every medical discipline?

    An important step towards truly meaningful “big data”


    An editorial by Walter Koroshetz, acting director

    Electronic data sharing infrastructure is now more accessible, the concept of “big data”
    has become popular. The investigator community can advance its science to another level by embracing the culture change and ensure that big data are good data. Establishing and using
    common outcome measures is the first step. Read the full editorial here.

  • Tuesday 06 January, 2015 - Survey of new 2007 and 2011 Cochrane reviews found 37% of prespecified outcomes not reported

    COS have been used rarely in Cochrane Reviews, but the introduction of SoF makes the development and application of COS timelier than ever. To explore these issues as part of our work within COMET, we have performed a survey of Cochrane Reviews to identify the variety of outcome measures used in them. Read the full paper here.

  • Monday 01 December, 2014 - Report from the COMET IV meeting Rome 19-21st Nov 2014 by Duncan Barron

    Duncan Barron - a blog post about the conference, the reasons for developing Core Outcome Sets (COS) and some of the presentations. Read the blog here.

Recently Added Studies

  • Core outcome sets for tuberculosis

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  • Developing a core outcome set (COS) for clinical trials in intrauterine growth restriction.

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  • A core outcome set for comparative effectiveness research in open lower limb fractures

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  • Variations in the reporting of outcomes used in systematic reviews of treatment effectiveness research in bladder pain syndrome

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  • Developing a core outcome set (COS) for clinical trials in gestational diabetes mellitus

    [View details]

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