Development of core outcome sets for interventions to improve informed consent for clinical trials

Outcome measurements reported in trials of interventions to improve the informed consent process for decisions about trial participation are heterogeneous, and, there is a lack of clarity regarding which outcomes matter and why. Therefore, generation of a ‘core outcome set’ could avoid problems such as outcome selection and reporting bias and allow more meaningful comparison across studies when synthesised together.

This project (part of a larger programme of work) will develop a core outcomes set for the evaluation of interventions intended to improve trial informed consent processes and trial recruitment experiences.



Dr Katie Gillies (PI) – Health Services Research Unit (HSRU), University of Aberdeen
Professor Marion Campbell, HSRU, University of Aberdeen
Professor Vikki Entwistle, HSRU, University of Aberdeen
Professor Shaun Treweek, HSRU, University of Aberdeen
Professor Paula Williamson, University of Liverpool

Further Study Information

Current Stage: Ongoing
Date: May 2014 - 2020
Funding source(s): MRC Methodology Research Fellowship (Dr Katie Gillies)

Health Area

Disease Category: Other

Disease Name: N/A

Target Population

Age Range: Unknown

Sex: Either

Nature of Intervention: Educational/self-management

Stakeholders Involved

- Clinical experts
- Consumers (patients)
- Ethicists
- Patient/ support group representatives
- Researchers
- Trialists

Study Type

- COS for clinical trials or clinical research


- Delphi process
- Systematic review

1. Systematic methodology review of existing outcome measures of trial informed consent interventions.

As per the internationally agreed COMET framework1, a review of the literature will be undertaken to provide an overview of the range of outcome measures used, and the methodology of their development and implementation. A formal search strategy will be developed in consultation with the HSRU Senior Information Scientist (see letter of support). The Cochrane Library, MEDLINE, EMBASE, CINAHL, ASSIA and PsycINFO will be searched for eligible studies. Citations identified through the initial screening search will be assessed by two people, with a third reviewer acting as an arbiter if there is disagreement. Full text papers will be obtained for those studies that on initial screening are considered potentially relevant and will be further assessed for inclusion. Reference lists of all included studies will be examined for further relevant studies. Information from primary studies will be abstracted and summarised on the following data: intervention; population; study design; scenario (e.g. real vs. hypothetical study); sample size; outcomes reported; and measurement tools used. This systematic methodology review will produce a list of all outcome variables reported in intervention studies of informed consent for trials. An initial scoping search identified only a small number of studies (n=8) that have measured relevant outcomes other than knowledge and recruitment in a trials context. The review findings will be supplemented with outcomes measured in the Cochrane review of decision aids to support patients’ decision making for treatment and screening.2 In addition, a critical analysis of articles that have discussed the issue of informed consent for research and any potentially relevant outcomes suggested will also be included (see for example references 3 & 4).

2. Exploration of additional outcomes relevant for trial participation decisions.

Thirty international expert stakeholders (e.g. patient advocates; trialists and research nurses; social scientists and ethicists with an interest in trials), numbers which are in line with guidance on sampling for Delphi interview studies30, will be invited to participate in semi-structured interviews in which their views on the outcomes identified thus far will be explored. A summary of findings from the literature review will be shared in advance and participants will be asked to suggest additional outcomes of relevance and why these outcomes could be important in a trial context. This will allow identification of outcomes that, as yet, have not been considered, or used, in empirical studies of interventions to improve the decision making process for trial participation. The interviews will be audio-recorded, transcribed, and thematically analysed using a modified framework approach, facilitated by NVivo.

3. Define core outcome set for evaluation of trial informed consent interventions.

The list of outcomes generated from the systematic review and interviews will form the basis of an international Delphi survey to refine the items into a core outcome set, as per the COMET methodology.1 The outcome list will be developed into an online questionnaire with items each to be rated on a Likert scale and also include a free text box. The rating process will involve the same stakeholder groups as in (Stage 2). Stakeholders will be invited to participate in the Delphi survey through email distribution lists and a purposive sample of 10 participants from each stakeholder group (see Stage 2) will be included in the rounds of rating. Participants will complete 2 rounds of rating with personalised feedback, both quantitative (frequency distribution of the group scores, the median and interquartile range, and individual participant’s previous scores) and qualitative (summary of comments), during round 2. Agreement will first be investigated across all respondents and then at stakeholder group level to allow equal weighting during the analysis so as to retain representativeness in the final item set.

1. Williamson PR, et al. Trials. 2012;13:132
2. Stacey D, et al. Cochrane Database Syst Rev. 2011;5(10)CD001431
3. Corrigan O. Sociol Health Illn. 2003;35(7):768.
4. Gillies K & Entwistle VA. J Med Ethics. 2012;38(12):751.
5. Asch SE. Sci Am. 1955;193:31