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Using the Delphi process to determine the minimum clinically important effect size for the Balanced-2 randomised

Carolyn Deng^1,2, David Sidebotham^2,3

¹Department of Anaesthesia and Perioperative Medicine, Auckland City Hospital, Auckland, New Zealand.

Clinical Trials (London, England)

|May 5, 2023

Summary

Calculating sample sizes for clinical trials requires defining the minimum clinically important effect size. This study used the Delphi approach to determine this value for a trial on postoperative delirium, achieving consensus among anaesthetists.

Keywords:

Delphi process effect size randomised controlled trials sample size calculation

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Area of Science:

Clinical Trials Methodology
Anesthesiology
Geriatric Medicine

Background:

Accurate sample size calculation is crucial for randomized controlled trials (RCTs) with binary outcomes.
Defining a realistic and clinically important effect size is essential for effective sample size determination.
Overestimating effect size can lead to underpowered studies, compromising reliable detection of true population effects.

Purpose of the Study:

To determine the minimum clinically important effect size for the Balanced-2 trial using the Delphi approach.
To achieve consensus among specialist anaesthetists on the effect size for comparing light versus deep general anaesthesia.
To inform sample size calculations for an RCT investigating postoperative delirium in older adults.

Main Methods:

The Delphi approach was employed, utilizing electronic surveys administered in multiple rounds.
Two distinct stakeholder groups of specialist anaesthetists were surveyed: hospital-based and clinical research experts.
Consensus was defined as greater than 70% agreement on the median minimum clinically important effect size.

Main Results:

The median minimum clinically important effect size was consistently determined as 5.0% across both stakeholder groups.
Consensus was achieved after the second round of the Delphi survey, with agreement rates of 74% and 82% in the respective groups.
The combined minimum clinically important effect size, incorporating both groups, was 5.0% (interquartile range: 3.0-6.5).

Conclusions:

The Delphi process offers a straightforward method for defining minimum clinically important effect sizes.
Establishing a consensus-based effect size is vital for accurate sample size calculations in RCTs.
This approach enhances the feasibility and reliability of randomized studies by ensuring appropriate sample sizes.