Core outcome set for preventive intervention trials in chronic and episodic migraine (COSMIG): an international, consensus-derived and multistakeholder initiative

Objective Typically, migraine prevention trials focus on reducing migraine days. This narrow focus may not capture all that is important to people with migraine. Inconsistency in outcome selection across trials limits the potential for data pooling and evidence synthesis. In response, we describe the development of core outcome set for migraine (COSMIG).

Design A two-stage approach sought to achieve international, multistakeholder consensus on both the core domain set and core measurement set. Following construction of a comprehensive list of outcomes, expert panellists (patients, healthcare professionals and researchers) completed a three-round electronic-Delphi study to support a reduction and prioritisation of core domains and outcomes. Participants in a consensus meeting finalised the core domains and methods of assessment. All stages were overseen by an international core team, including patient research partners.

Results There was a good representation of patients (episodic migraine (n=34) and chronic migraine (n=42)) and healthcare professionals (n=33) with high response and retention rates. The initial list of domains and outcomes was reduced from >50 to 7 core domains for consideration in the consensus meeting, during which a 2-domain core outcome set was agreed.

Conclusion International and multistakeholder consensus emerged to describe a two-domain core outcome set for reporting research on preventive interventions for chronic and episodic migraine: migraine-specific pain and migraine-specific quality of life. Intensity of migraine pain assessed with an 11-point Numerical Rating Scale and the frequency as the number of headache/migraine days over a specified time period. Migraine-specific quality of life assessed using the Migraine Functional Impact Questionnaire.


Kirstie Haywood, Rachel Potter, Robert Froud, Gemma Pearce, Barbara Box, Lynne Muldoon, Richard Lipton, Stavros Petrou, Regina Rendas-Baum, Anne-Marie Logan, Kimberley Stewart, Martin Underwood, Manjit Matharu on behalf of the CHESS COSMIG group


Journal: BMJ Open
Volume: 11
Issue: e043242
Pages: -
Year: 2021
DOI: 10.1136/bmjopen-2020-043242

Further Study Information

Current Stage: Completed
Date: January 2017 - January 2018
Funding source(s): National Institute for Health Research (NIHR) Programme Grants for Applied Research programme (RP-PG-1212-20018)

Health Area

Disease Category: Neurology

Disease Name: Headache, Migraine

Target Population

Age Range: 18 - 100

Sex: Either

Nature of Intervention: Any

Stakeholders Involved

- Charities
- Clinical experts
- Consumers (patients)
- Economists
- Methodologists
- Patient/ support group representatives
- Researchers
- Service users

Study Type

- COS for clinical trials or clinical research
- Recommendations for outcome measures (measurement/how)


- Consensus meeting
- Delphi process
- Interview
- Literature review
- Nominal group technique (NGT)
- Systematic review

Three key stages are proposed:
1. A comprehensive list of outcomes will be developed to inform questionnaire development for the international e-Delphi.
a. This will be informed by systematic reviews completed as part of the CHESS study.
b. Qualitative research and narrative reviews completed as part of the CHESS study.
c. A long-list of potential outcomes will be considered, mapped onto health domains and discussed with key stakeholders, including patient research partners.
d. A final list of outcomes and domains will inform items for the e-Delphi (stage 2).

2. A three-round international e-Delphi survey is proposed to work towards consensus on the core domain set (CDS).
a. International participants will be identified – to reflect key stakeholders including health professionals, clinicians, patients, clinical academics, researchers.

3. An international, multi-stakeholder consensus meeting (modified nominal group) will be held to confirm the core domain set (CDS) and to achieve consensus on the core outcome measurement set (COMS).

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