Background
A core outcome set (COS) is an agreed, standardised collection of outcomes that key stakeholders have agreed should be measured as a minimum in all trials and other studies for specific health conditions [The Delphi method aims to incorporate the positive aspects of group participation, such as input from different viewpoints and expertise, without the negative constraints of social interactions in face-to-face settings [The Delphi approach is characterised by several factors, including ‘anonymity, iteration, controlled feedback, and statistical aggregation of group response’ [A Delphi survey also allows participants to contribute views or new ideas for survey questions. This information can be moderated by the survey administrator and presented to other participants for comment or voting [In the context of COS development, the Delphi survey involves iterative rounds of an online survey whereby outcomes are listed and participants are asked to rate their importance, typically on a 9-point Likert scale [Although the Delphi method is commonly used to achieve consensus on what outcomes are ‘core’ in COS development, shortfalls with the approach have been noted [In recent years, the concept of a ‘Real-Time’ Delphi (RTD) has emerged. The functionality of a RTD can potentially improve the shortfalls of engaging in a long Delphi survey process with multiple rounds [Gnatzy et al. [