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Difference ELicitation in TriAls (DELTA)

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Summary

The randomised controlled trial (RCT) is widely considered to be the gold standard study for comparing the effectiveness of health interventions. From both a scientific and ethical standpoint, selecting an appropriate target difference is of crucial importance. Given its importance, determination of the target difference, as opposed to statistical approaches to calculating the sample size, has been greatly neglected. A variety of approaches have been proposed for formally determining what an important difference should be (such as the "minimum clinically important difference") though the current state of the evidence is unclear particularly with regards to informing RCT design. This project will seek to provide an overview of the current evidence through three main components: (i) a systematic review of methods for identifying a target difference developed within and outside the health field to assess their usefulness for various forms of RCTs; (ii) current 'best' trial practice will be evaluated using a survey of trialists (including UK Clinical Trial Units and MRC Trial Hubs); and (iii) a structured guidance document will be produced to aid the design of future trials.

This project is led by Dr Jonathan Cook from HSRU with collaborators from the Universities of Aberdeen, East Anglia, Glasgow, Newcastle and Oxford in the UK and the National University of Ireland in Galway, and the Ottawa Health Research Institute in Canada. It is funded by the UK Medical Research Council and NIHR.

Contact

Jonathan Cook; j.a.cook@abdn.ac.uk

Status

Ongoing

Further Information

Methods for determining the target difference for a randomised controlled trial

Publications

Cook JA, Ramsay CR, Vale LD, DELTA group. Guidance on minimally important clinical difference and trial size is needed [letter]. BMJ 2012;343:-D4375.