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 774 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 29 February, 2016 - COMET VI Save the date

    We are pleased to announce that COMET VI will take place on Thursday 10th and Friday 11th November 2016, in Amsterdam.

    The venue name is Rode Hoed (it means red hat and is named after the hat makers that were there before the church was built).

    More details and registration to follow, but for now SAVE THE DATE!

  • Monday 25 January, 2016 - Core outcome sets and systematic reviews

    Systematic reviews seek to bring together research evidence to answer the question for the review. The reviewers usually wish to compare, contrast and, if appropriate, combine the findings of the existing research studies. However, these intentions are often thwarted by inconsistencies in the outcomes that were measured and reported in the individual studies. This, in turn, makes it difficult for readers of the review to use it to make informed decisions and choices about health and social care. One solution is for trials in a particular topic area to measure and report a standardised set of outcomes, which would then be used in the review. Core outcome sets are a means of doing this. Read the full commentary here.

  • 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

  • Enhanced Patient Involvement and the Need to Revise the Core Set - Report from the Psoriatic Arthritis Working Group at OMERACT 2014

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  • Review of the Psoriatic Arthritis Working Group at OMERACT 12: A Report from the GRAPPA 2014 Annual Meeting

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  • Update on Outcome Measure Development for Large Vessel Vasculitis: Report from OMERACT 12

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  • The German national consensus on wound documentation and outcomes: Rationale, working programme and current status

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  • Identifying the most important outcomes for systematic reviews of interventions for rhinosinusitis in adults: working with Patients, Public and Practitioners*

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