Specifying the target difference in the primary outcome for a randomised controlled trial: guidance for researchers

Cook, J. A. et al. (2015) Specifying the target difference in the primary outcome for a randomised controlled trial: guidance for researchers. Trials, 16(1), 12. (doi:10.1186/s13063-014-0526-8) (PMID:25928502) (PMCID:PMC4302137)

[img]
Preview
Text
102622_coversheet.pdf - Cover Image

79kB
[img]
Preview
Text
102622.pdf - Published Version
Available under License Creative Commons Attribution.

441kB

Abstract

Background: Central to the design of a randomised controlled trial is the calculation of the number of participants needed. This is typically achieved by specifying a target difference and calculating the corresponding sample size, which provides reassurance that the trial will have the required statistical power (at the planned statistical significance level) to identify whether a difference of a particular magnitude exists. Beyond pure statistical or scientific concerns, it is ethically imperative that an appropriate number of participants should be recruited. Despite the critical role of the target difference for the primary outcome in the design of randomised controlled trials, its determination has received surprisingly little attention. This article provides guidance on the specification of the target difference for the primary outcome in a sample size calculation for a two parallel group randomised controlled trial with a superiority question.<p></p> Methods: This work was part of the DELTA (Difference ELicitation in TriAls) project. Draft guidance was developed by the project steering and advisory groups utilising the results of the systematic review and surveys. Findings were circulated and presented to members of the combined group at a face-to-face meeting, along with a proposed outline of the guidance document structure, containing recommendations and reporting items for a trial protocol and report. The guidance and was subsequently drafted and circulated for further comment before finalisation.<p></p> Results: Guidance on specification of a target difference in the primary outcome for a two group parallel randomised controlled trial was produced. Additionally, a list of reporting items for protocols and trial reports was generated.<p></p> Conclusions: Specification of the target difference for the primary outcome is a key component of a randomized controlled trial sample size calculation. There is a need for better justification of the target difference and reporting of its specification.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Briggs, Professor Andrew and Ford, Professor Ian
Authors: Cook, J. A., Hislop, J., Altman, D. G., Fayers, P., Briggs, A. H., Ramsay, C. R., Norrie, J. D., Harvey, I. M., Buckley, B., Fergusson, D., Ford, I., and Vale, L. D.
College/School:College of Medical Veterinary and Life Sciences > Institute of Health and Wellbeing > Robertson Centre
College of Medical Veterinary and Life Sciences > Institute of Health and Wellbeing > Health Economics and Health Technology Assessment
Journal Name:Trials
Publisher:BioMed Central
ISSN:1745-6215
ISSN (Online):1745-6215
Copyright Holders:Copyright © 2015 The Authors
First Published:First published in Trials 16(1):12
Publisher Policy:Reproduced under a Creative Commons License

University Staff: Request a correction | Enlighten Editors: Update this record

Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
532861Assessing methods to specify the targeted difference for a randomised controlled trial (the DELTA Study)Andrew BriggsMedical Research Council (MRC)G0902147IHW - HEALTH ECON & TECH ASSESSMENT