Core Outcome Set for Chronic Fatigue Syndrome/Myalgic Encephalomyelitis

Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) a long-term, complex, debilitating disorder associated with poor health-related quality of life and declined functional status for individuals and a significant economic burden on society. CFS/ME is defined by symptoms and patient’s constraints on daily living is influenced directly by symptoms.

We will develop a core outcome set for CFS/ME following recommendations for developing core outcome set (COS) from COMET (Core Outcome Measures in Effectiveness Trials), COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments), and OMERACT (Outcome Measures in Rheumatology). We will conduct two scoping reviews of qualitative research and interventional studies. To select the most important outcome measures for CFS/ME, after the evidence synthesis, we will use the Delphi process involving patient partners and clinicians in this area and a modified Nominal Group Technique to achieve consensus. The COS for CFS/ME will inform outcomes that are measured and reported in future studies in this area, including systematic reviews, clinical trials, and clinical practice guidelines.


Dena Zeraatkar and Jason Busse from McMaster University, Hamilton, Canada

Further Study Information

Current Stage: Ongoing
Date: August 2022 - December 2022
Funding source(s): None

Health Area

Disease Category: Other

Disease Name: Chronic Fatigue Syndrome, Myalgic Encephalomyelitis

Target Population

Age Range: 18 - 120

Sex: Either

Nature of Intervention: Drug, Nonpharmacological

Stakeholders Involved

- Clinical experts
- Epidemiologists
- Patient/ support group representatives
- Researchers

Study Type

- COS for clinical trials or clinical research
- COS for practice


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

We will follow recommendations for developing COS from COMET, COSMIN, and OMERACT initiatives based on scoping reviews and consensus through the Delphi process. The methods will include the following four steps. 1) Scoping review of qualitative research with CFS/ME patients addressing domains of care and health that are most important to them; 2) Scoping review of interventional studies (randomized controlled trials) in CFS/ME and outcome measures; 3) Categorization of outcomes into domains; 4) Delphi process for selecting the most important domains and outcome measures; 5) Modified Nominal Group Technique to achieve consensus.

Scoping reviews
With the aid of an experienced research librarian, we will search MEDINE, EMBASE, and Cochrane CENTRAL and other relevant databases from inception to August 2022 for qualitative or mixed-methods studies that queried CFS/ME patients related to important aspects of their care and outcomes (scoping review 1) and randomized trials that addressed the comparative effectiveness of pharmacologic and non-pharmacologic interventions for patients with CFS/ME (scoping review 2). We will not restrict eligibility based on criteria for diagnosis of CFS/ME, type of intervention, or language or date of publication.

To identify eligible studies, trained reviewers will work in pairs and independently perform titles/abstracts and full-texts screening. Subsequently, reviewers, working independently and in duplicate, will perform data extraction. Reviewers will resolve discrepancies by discussion or, when necessary, by adjudication with a third party. For scoping review of randomized trials, we will collect data on the type of randomized trial (i.e., individually randomized versus cluster versus crossover), publication type (i.e., preprint versus publication), whether patients were involved in the design of randomized trials, the number of patients, patient characteristics, interventions studied, and outcomes addressed (i.e., construct measured, domains, range of scale, minimally important difference, outcome assessor, reason for selection, timepoints assessed). For scoping r of qualitative studies, reviewers will extract information to capture the individual's experience of a symptom/phenomenon and how they understand their experiences about outcomes measures and interventions.

Outcome Categorization
We will present data qualitatively and quantitatively to synthesize our findings. We will categorize outcomes into domains of health.

Delphi process
We will construct a survey including the list of potential outcomes from our scoping reviews of outcomes and distribute the survey to patients with CFS/ME and clinicians who treat patients with CFS/ME. We will ask participants to rate the outcomes based on importance using a 9-point Likert scale, from 1 (not at all important) to 9 (critical) and to add and rate the importance of any outcomes that they felt were important but were not captured in the list. We will iterate the Delphi process several times (depending on the survey results and feedback) to attain the preliminary COS.

Modified Nominal Group Technique and consensus meeting

We will discuss the advantage and disadvantages of the preliminary COS at large group meetings with patients and clinicians. We will send the findings of the scoping review and the preliminary COS at least one week before the formal discussion. One core author will also present the main findings, the preliminary COS, and the objective of the group discussion. One of the steering team members will facilitate the meeting discussion in person or through video conferences. During the meeting, first, we require participants to write down their general ideas or critiques for the framework in silence. Second, we allow participants to share their ideas, critiques, arguments, or examples. Last, we let all participants vote and/or agree on the final preliminary COS. The final agreement requires at least eighty percent agreement. All members have two weeks following the request for approval to submit additional comments.

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