Core Outcome Measures in Effectiveness Trials

Developing a core outcome set for interventions to enhance proxy decisions about research on behalf of adults who lack capacity to consent: COnSiDER

General Information

There has been a growing focus on interventions to improve the informed consent process for decisions about trial participation. For adults who lack capacity to provide informed consent for themselves, substitute or proxy decision-makers are involved in decisions about their participation in trials. Proxy decisions about trial participation are challenging and may also benefit from interventions to enhance the decision-making process. However, establishing which outcomes matter, to whom, and why has not yet been explored.

Due to the differences in ‘self/other’ decision-making, outcomes for proxy decisions about trial participation may differ markedly from those reported in trials of interventions to improve informed consent for decisions about trial participation. Therefore, establishing what conceptually constitutes ‘good’ proxy decisions about research, and the generation of a core outcome set, will support the development and subsequent evaluation of interventions.

This project (part of a larger programme of work) will develop a core outcome set for the evaluation of interventions to enhance proxy decisions about research on behalf of adults who lack capacity to consent.

Victoria Shepherd (PI), Centre for Trials Research, Cardiff University
Prof Kerry Hood, Centre for Trials Research, Cardiff University
Dr Fiona Wood, Division of Population Medicine, Cardiff University
Prof Michael Robling, Centre for Trials Research, Cardiff University
Liz Randell, Centre for Trials Research, Cardiff University

Further Study Information

Current Stage:
August 2019 - August 2020
Funding source(s):
Part funded by NIHR Doctoral Research Fellowship (V Shepherd) funded by Health and Care Research Wales

Health Area

Disease Category

Disease Name

Target Population

Age Range


Nature / type of Intervention


Consensus meeting
Delphi process
Literature review
Systematic review

The core outcome set (COS) will be developed in accordance with the COMET guidance [1] and adapted to take account of the nature the phenomenon and novelty of the intervention being investigated. The project will be conducted in three stages:

1. Concept synthesis
The first step is to conceptualise for the first time what constitutes a ‘good’ or high-quality proxy decision about research. Concept synthesis is a mechanism for generating a new concept of theory through drawing together data from sources such as literature and qualitative and quantitative research to provide new insights into a phenomenon [2]. A literature review will be undertaken to explore the conceptual aspects of decision quality relating to proxy decision-making for research and to identify candidate outcome domains. The literature review will explore what are considered to be the constituents of proxy decision-making (i.e the process) and decision quality (i.e the decision itself) and identify domains which capture these aspects. The concepts will inform the search strategy for the scoping review and provide context within which the outcomes can then be identified and considered for inclusion in the COS.

2. Scoping review
Secondly, as no previous interventions have been developed or evaluated for proxy decisions about research, a scoping review [3] will be conducted to identify candidate outcomes and outcome measures used in trials of other relevant decision support interventions. A search strategy will be developed to identify studies reporting outcomes and outcome measures used for evaluating interventions to improve consent in trials, and studies evaluating decision support interventions to improve proxy decision-making for care/medical treatment. Database searches will include MEDLINE, Cochrane Central, and PsycINFO. Outcomes will be identified and collated for consensus in the third part of the project. Identified outcome measures will be assessed for quality and mapped against the outcome domains identified. Any areas of absence (i.e where there were no outcome measures found for domains identified as relevant in the scoping review or literature review) will be highlighted.

3. Stakeholder consultation
Thirdly, consensus on the most relevant and important outcomes will then be sought with relevant stakeholder groups through a Delphi survey and consensus event. A group of approx. 20 stakeholders (e.g. research nurses, researchers, patients and families/carers, and ethicists with an interest in informed consent/trials) will be invited to participate. In Round 1 the outcome list will be developed into an online questionnaire with items to be rated using a Likert scale, including a free text box for participants to provide include any additional outcomes that have not been included in the list. All outcomes (including any new outcomes identified in Round 1) will be carried forward to the next round. In Round 2, participants will be asked to rescore all outcomes and consider whether they should be included in a core outcome set, with a text box provided for an explanatory comment. In both rounds descriptive statistics will be used to summarise the number of participants who scored each item and the distribution of scores, alongside the number of respondents who scored the items across both rounds, with consensus defined a priori.

The final phase of the consultation will be a face-to-face meeting with key stakeholder participants from the Delphi survey to reach consensus on the items to be included in the core COS. Data from the Delphi survey will be presented for discussion, and agreement reached on the final list of outcomes that will constitute the COS. Following the consensus meeting the final stage of the study is to determine which instruments should be used to measure the identified outcomes. The list of candidate measures identified during the scoping review will be reviewed against the outcome domains identified for inclusion during the Delphi consensus process. Any outcomes for which no appropriate instruments have been identified will be the target for future outcome measure development.

[1] Williamson PR, Altman DG, Bagley H, Barnes KL, Blazeby JM, Brookes ST, et al. The COMET Handbook: version 1.0. Trials. 2017;18:280
[2] Walker, LO, Avant, KC. Strategies for Theory Construction in Nursing. 6th Edition. Harlow: Pearson Education Ltd; 2019
[3] Peters MDJ, Godfrey CM, Khalil H, McInerney P, Parker D, Soares CB. Guidance for conducting systematic scoping reviews. International Journal of Evidence-Based Healthcare. 2015;13:141

Stakeholders Involved

Consumers (caregivers)
Consumers (patients)
Patient/ support group representatives
Research nurses

Study Type

COS for clinical trials or clinical research

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