P056 Power Calculations in Randomised Controlled Trials of Inflammatory Bowel Disease

Abstract

Background:
Sample size estimation is a vitally important calculation to make when designing a clinical trial. 25% of randomised controlled trials (RCTs) on interventions for Inflammatory Bowel Disease (IBD) have no power calculation (PC). We set out to systematically review RCTs reporting interventions for the management of IBD and to use the actual clinical data across these comparisons to produce data for minimum sample sizes that would achieve appropriate power.

Methods:
We included RCTs investigating any form of therapy for the treatment of IBD in patients of any age and interventions for either induction or maintenance of remission against control, placebo, or no intervention. The relevant data was extracted, and the studies were grouped according to the intervention used. We recalculated sample size and the achieved difference, as well as minimum sample sizes needed in the future.

Results:
A total of 105 trials were included. There was a large discrepancy between the estimated figure for the minimal clinically important difference used for power calculations and the actual differences seen. The minimum sample sizes to use in future trials were proposed based on the calculations made from actual achieved clinical differences from previous studies.

Conclusion:
A third of intervention studies in IBD within the last 25 years are underpowered, with large variations in the calculation of sample sizes. The resource containing sample size estimates constructed on the published evidence base is required for future researchers and key stakeholders within the IBD trial field.