Core Outcome Measures in Effectiveness Trials

COMET Initiative

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 1137 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 14 January, 2019 - 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 info@comet-initiative.org

  • Monday 14 January, 2019 - Fourth annual update to a systematic review of core outcome sets for research

    We have now completed the fourth update to a systematic review of COS, identifying COS published and indexed in 2017. This update identified 48 new COS articles that describe 56 new COS. This is a marked increase in the number of new COS identified in the previous three updates, which included 28, 20 and 15 new COS publications (describing the development of 29, 20 and 15 COS) respectively.

  • Monday 14 January, 2019 - Higher number of items associated with significantly lower response rates in COS Delphi surveys

    The Delphi method is commonly used to achieve consensus in core outcome set (COS) development. It is important to try to maximize response rates to Delphi studies and minimize attrition rates and potential for bias. The factors that impact response rates in a Delphi study used for COS development are unknown. The objective of this study was to explore the impact of design characteristics on response rates in Delphi surveys within COS development.

Recently Added Studies

  • Development of a Core set of outcomes for exercise and physical activity interventions supporting people with musculoskeletal disorders.

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  • coreSCD: Core Outcomes in Sickle Cell Disease

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  • Development of a core outcome set for clinical trials in primary dysmenorrhea:study protocol for a systematic review of the literature and identification of a core outcome set using a Delphi survey

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  • Developing a Core Outcome Set for Traditional Chinese Medicine on Treatment of Ischemic Stroke

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  • Developing a Core Outcome Set of Traditional Chinese Medicine for abdominal Henoch Schonlein purpura in Children

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