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 934 references of planned, ongoing and completed work.

The keyword used for the search will be compared with study title, abstract and author's surname.

View full search options

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

  • Thursday 23 February, 2017 - 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

  • Thursday 23 February, 2017 - Call out for funding contacts overseas

    As part of COMET's strategic plan, we are looking to find ways to raise awareness about core outcome sets and the COMET Initiative amongst research funding agencies. We are trying to identify representatives from different countries who are best placed to start that dialogue with funders in their country. If you are interested in becoming involved, please do get in touch.  As an example from the UK, the NIHR HTA guidance documents includes the following text about outcomes, for people submitting a funding application through one of their work streams (see section 7.2)
    "Where established Core Outcomes exist they should be included amongst the list of outcomes unless there is good reason to do otherwise. Please see The COMET Initiative website at to identify whether Core Outcomes have been established."

  • Wednesday 21 September, 2016 - How to select outcome measurement instruments for outcomes included in a "Core Outcome Set" - a practical guideline.

    A new consensus based guideline for selecting outcome measurement instruments has recently been published in Trials.

    In collaboration with the COMET Initiative, the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) initiative have developed a guideline on how to select outcome measurement instruments for outcomes (i.e., constructs or domains) included in a "Core Outcome Set" (COS). This guideline can be used by COS developers in defining how to measure core outcomes.

    Read the full paper here.

Recently Added Studies

  • International and Interdisciplinary Identification of Health Care Transition Outcomes

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  • Outcome measures for artificial pancreas clinical trials: A consensus report

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  • Connective Tissue Disease-associated Interstitial Lung Diseases (CTD-ILD) - Report from OMERACT CTD-ILD Working Group

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  • Developing a core set of patient-reported outcomes in pancreatic cancer: A Delphi survey

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  • Clinicians’ perspective on key domains in ANCA-associated vasculitis: a Delphi exercise

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