“Vicarious thinking” is a key driver of score change in Delphi surveys for COS development and is facilitated by feedback of results

Rebecca Fish* (Corresponding Author), Steven MacLennan, Bilal Alkhaffaf,, Paula R. Williamson

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)
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The objectives of this nested study were to (1) assess whether changes in scores between rounds altered the final degree of consensus achieved in three Delphi surveys conducted as part of COS development projects (anal, gastric and prostate cancer), and (2) explore participants’ reasons for changing scores between rounds
Study design and setting:
All Delphi surveys were conducted online using DelphiManager software and included healthcare professionals and patient participants. Participants were invited to give a free-text reason whenever they changed their score across an importance threshold in a 1-9 Likert scale (1-3 not important, 4- 5 important, 7-9 critically important). Reasons for score change were coded by four researchers independently using an inductive-iterative approach.
In all three Delphi surveys, the number of outcomes reaching criteria for consensus was greater in R2 than R1. Twelve themes and 23 sub-themes emerged from 2298 discrete reasons given for score change. The most common reasons for change were ‘time to reflect’ (482 responses, 23%) and
vicarious thinking (424, 21%), with 68% (291) of vicarious thinking attributed to seeing other participants scores.
Our findings support conducting a Delphi survey over the use of a single questionnaire where building consensus is the objective. Time to reflect and vicarious thinking, facilitated by seeing other participants scores, were important drivers of score change. How results are presented to participants between rounds and the duration of and time between rounds in a Delphi survey may
therefore influence the results and should be clearly reported.
Original languageEnglish
Pages (from-to)118-129
Number of pages12
JournalJournal of Clinical Epidemiology
Early online date30 Sept 2020
Publication statusPublished - 1 Dec 2020

Bibliographical note

We would like to thank and acknowledge the participants in the Delphi surveys used here. We also thank individuals who contributed significantly to the wider COS development projects: Professor Andrew G. Renehan and Professor Caroline Sanders (CORMAC); Dr. Thomas B. L. Lam (COMPACTERS); Professor Iain A Bruce and Professor Jane M Blazeby (GASTROS).
This work was supported by a National Institute for Health Research (NIHR) Senior Investigator Award (NF-SI_0513-10025). The views expressed in this article are those of the authors and not necessarily those of the NIHR, or the Department of Health and Social Care.


  • Core outcome set development
  • Delphi survey
  • consensus
  • stakeholders
  • feedback methods


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