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 1256 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

  • Monday 04 March, 2019 - MRC-NIHR Trials Methodology Research Partnership

    Multiple PhD studentships, various locations across the UK         

    2019 entry

    The MRC-NIHR Trials Methodology Research Partnership (TMRP) brings together a number of national and international networks, institutions and partners undertaking clinical trials and trials methodology research. The overall aim being to improve patient care by improving the way in which the healthcare evidence base is developed. The PhD programme presents a unique opportunity to undertake training and research in major areas where clinical trials need to be improved to help increase the health of society. Projects are available at locations across the UK for candidates with qualifications in a variety of subject areas including statistics, mathematics, health economics, epidemiology, psychology, social science, computer science, informatics and health services research.

    Details of projects, institutions and supervisors currently available can be found here:

    http://methodologyhubs.mrc.ac.uk/about/phd-studentships

    COS themed projects can be found here:

    https://www.liverpool.ac.uk/translational-medicine/departmentsandgroups/biostatistics/phd-studentships/

  • 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

  • Core Outcome Measures for Research in Critically Ill Patients Receiving Extracorporeal Membrane Oxygenation for Acute Respiratory or Cardiac Failure: An International, Multidisciplinary, Modified Delphi Consensus Study

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  • Core Outcome Measures in Paediatric sepsis in low middle-income countries

    [View details]
  • Core Outcome Set for trials on the prevention and treatment of enamel White Spot Lesions (COS-WSL)

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  • The development of a core outcome set for pouch anal fistula - An international Delphi study

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  • Outcome and comparator choice in molar incisor hypomineralisation (MIH) intervention studies: a systematic review and social network analysis

    [View details]

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