Core Outcome Measures in Effectiveness Trials

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 652 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

  • Monday 01 June, 2015 - Abstracts of the 4th Meeting of the Core Outcome Measures in Effectiveness Trials (COMET) Initiative

    Abstracts and a meeting summary are now published in Trials. View the supplement here.

  • Friday 22 May, 2015 - Towards core outcome set (COS) development: a follow-up descriptive survey of outcomes in Cochrane reviews

    As part of this work, an earlier exploratory survey of the outcomes of newly published 2007 and 2011 Cochrane reviews was performed. This survey examined the use of COS, the variety of specified outcomes, and outcome reporting in Cochrane reviews by Cochrane Review Group (CRG). To examine changes over time and to explore outcomes that were repeatedly specified over time in Cochrane reviews by CRG, we conducted a follow-up survey of outcomes in 2013 Cochrane reviews. The proportion of specified outcomes that were reported in Cochrane reviews had increased in 2013 (68 %) compared to 2007 (61 %) and 2011 (65 %). Importantly, 2013 Cochrane reviews that did not report specified outcomes were twice as likely to provide an explanation for why the outcome was not reported. There has been an increased uptake of SoF tables in Cochrane reviews. Outcomes that were repeatedly specified in Cochrane reviews by CRG in 2007, 2011, and 2013 may assist COS development.Read the full paper here.

  • Wednesday 20 May, 2015 - International Clinical Trials Day 2015

    If trials are to change lives, their findings need to focus on the outcomes that really matter to people making decisions about health and social care. One of the ways to do this is through the use of core outcome sets that should be used across all trials in a particular area of health. The COMET Initiative is helping to support this, and Liz Gargon from the University of Liverpool in the UK updates us on their work. Listen to the podcast here.

Recently Added Studies

  • A systematic review of outcome measures employed in aneurysmal subarachnoid haemorrhage clinical research

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  • Establishing a core outcome set (COS) for infants born with gastroschisis

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  • Meaningful health outcomes for paediatric neurodisability: Stakeholder prioritisation and appropriateness of patient reported outcome measures

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  • What matters to patients? A systematic review of preferences for medication-associated outcomes in mental disorders

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  • A systematic review of the outcomes reported in multimodal pain therapy for chronic pain

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