Systematic Reviews
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 21, 2021; 27(43): 7572-7581
Published online Nov 21, 2021. doi: 10.3748/wjg.v27.i43.7572
Minimum sample size estimates for trials in inflammatory bowel disease: A systematic review of a support resource
Morris Gordon, Svetlana Lakunina, Vasiliki Sinopoulou, Anthony Akobeng
Morris Gordon, Svetlana Lakunina, Vasiliki Sinopoulou, Biomedical Evidence Synthesis and Translation to Practice Unit, School of Medicine, Preston PR1 7BH, United Kingdom
Anthony Akobeng, Division of Gastroenterology, Sidra Med and Res Ctr, Doha 26999, Qatar
Author contributions: Gordon M conceived the study, contributed to design, analysis and writing; Lakunina S led completion, analysis and write up; Sinopoulou V and Akobeng A contributed to analysis, reviewed and edited the write up.
Conflict-of-interest statement: None to declare.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Morris Gordon, MBChB, PhD, Professor, Biomedical Evidence Synthesis and Translation to Practice Unit, School of Medicine, HA340, Harrington Building, 135A Adelphi St, Preston PR1 7BH, United Kingdom.
Received: March 4, 2021
Peer-review started: March 4, 2021
First decision: June 3, 2021
Revised: June 30, 2021
Accepted: October 31, 2021
Article in press: October 31, 2021
Published online: November 21, 2021
Research background

A third of randomised controlled trials (RCTs) on interventions for inflammatory bowel disease (IBD) have no adequate power calculation (PC).

Research motivation

A key element of PCs is an estimation of a minimally important clinical difference. The basis of these is capricious within the literature, with many not based on any existing or prior studies and as such can lead to massive shifts in PCs for similar studies, with concerns as to the underlying power.

Research objectives

We systematically reviewed RCTs reporting interventions for the management of IBD and to producted a resource for minimum clinically important difference using clinical data for the future researchers to use as a starting point.

Research methods

We included RCTs retrieved from Cochrane IBD trial register and CENTRAL investigating anti-inflammatory, immunomodulator and biologic therapies for either induction or maintenance of remission against control, placebo, or no intervention of IBD in patients of any age. The data was extracted and synthesized. We recalculated sample size and the achieved difference, as well as minimum sample sizes and presented in a tabular format.

Research results

Of 105 trials were included. A large discrepancy between the estimated figure for the minimal clinically important difference used for the calculations (15% differences observed vs 30% used for calculation) was observed explaining substantial actual sample size deficits. The minimum sample sizes indicated for future trials based on the 25 years of trial data were calculated and grouped by the intervention.

Research conclusions

There are large variations in the sample size calculatins in the studies of interventions for IBD with a third of all studies being underpowered. The authors present a sample size estimate resource constructed on the published evidence base for future researchers and key stakeholders within the IBD trial field.

Research perspectives

The use of this resource will support research staff, ethics committees and journal editors in ensuring adequate sample sizing and powering of studies across the field.