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’ (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.

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 814 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 11 July, 2016 - Including patients in core outcome set development: issues to consider

    The authors report on three interactive workshops that explored how patients and the public can contribute to decision making about what outcomes should be included in a COS. About 100 international delegates, including researchers, clinicians and patients, attended the workshops. The workshops were held in the United Kingdom, Italy and Canada as part of the COMET (Core Outcome Measures in Effectiveness Trials) Initiative annual meetings. Read the full paper here.

  • Thursday 30 June, 2016 - COMET VI registration now open

    We are pleased to announce that registration for COMET VI is now open. You can register here.

    You can also submit an abstract for presentation at COMET VI.

    We look forward to seeing you in Amsterdam.

  • Monday 25 January, 2016 - Choosing Important Health Outcomes for Comparative Effectiveness Research: An Updated Review and User Survey

    This study aimed to provide an update of a previous review, and examine the quality of development of COS. A further aim was to understand the reasons why individuals are searching the COMET database. This update demonstrates that recent studies appear to have adopted a more structured approach towards COS development and public representation has increased. The pop-up survey revealed the most common reasons for visiting the COMET website to be thinking about developing a COS and planning a clinical trial. Read the full paper here.

Recently Added Studies

  • Guidelines for the definition of time-to-event end points in renal cell cancer clinical trials: results of the DATECAN

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  • A Core Outcome Set for Children With Feeding Tubes and Neurologic Impairment: A Systematic Review

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  • Developing a Core Outcome Set for evaluating self-management interventions in people with comorbid diabetes and severe mental illness

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  • Stroke Recovery and Rehabilitation Roundtable (SRRR): consensus development for core measures in rehabilitation/recovery clinical trials

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  • Combining nutrition and exercise to optimize survival and recovery from critical illness: Conceptual and methodological issues

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