1. Opportunities for evaluation using the Stepped Wedge trial design Celia Brown, Alan Girling, Prakash Patil and Richard Lilford Department of Public Health and Epidemiology

2. Today’s presentation Describe the stepped wedge design Detail when the design might be useful Consider the advantages and disadvantages of the design Review 12 studies employing a stepped wedge design

3. The Stepped Wedge Design One individual/cluster receives the intervention in each time period Order of intervention determined at random All individuals/clusters get the intervention by the end of the process Data collected in each time period

4. When is the design useful? Prior belief that the intervention will do more good than harm – ethics of exclusion Logistical, practical or financial constraints to simultaneous intervention Evaluating a public policy intervention that is being rolled-out before effectiveness demonstrated (e.g. Sure Start)

5. Advantages Enables RCT approach in situations where parallel design not possible Can model the effect of time of intervention on effectiveness Can model the effect of length of intervention on effectiveness

6. Disadvantages Requires extensive data collection, so best where routine data are to be used Additional time analyses only appropriate if no cluster effect or cluster x time interactions Currently no published guide to data analysis (but watch this space!)

7. Review of Stepped Wedge studies Comprehensive literature search found only 12 papers or protocols:

8. Randomisation and Sample Size AuthorLevel of steppingRandomised?No. StepsSS Calc reported? InterventionControl Gambia Hepatitis Study Group Vaccination teamYes1761,06563,512 Yes CookCohortYes2No WilminkIndividualYes13,14729,713 person years 70,298 person yearsNo SomervilleSets of housesYes2No FairleyNot statedYes43No HughesPre-natal clinicNot stated2Aim: 304 Yes LevyIndividualYesNot statedNo PriestlyWardYes – in pairs82,9034,547Yes BaileyDistrictNot stated4No GrantIndividualYes1,655No CilibertoRehab unitNot stated7992186Yes ChaissonClinicYes29No 400 1,655 Not stated No. Participants 371 119 43 68

9. Reported motivations Ethical (n=4) Practical problems of simultaneous intervention (n=4): insufficient resources (n=3); logistical difficulties (n=2) Maintain RCT for evaluation (n=4) Detect underlying trends/control for time (n=4) Individuals/clusters act as own controls (n=2) None (n=1)

10. Methods of Data Analysis

11. Conclusions: Design Stepped wedge design has significant potential for evaluating public policy interventions using a RCT Intensive data collection means design most appropriate where routine data used Opportunities for assessing different effects of time

12. Conclusions: Review Review highlighted dearth of evaluations using the stepped wedge design Variety of interventions and settings establishes design’s potential Need to ensure studies reported to same standards as other trials (e.g. CONSORT) – particularly sample size calculations Variety of statistical approaches to data analysis implies need for standardised approach

13. Questions? Celia Brown: c.a.brown@bham.ac.ukc.a.brown@bham.ac.uk 0121 414 6043 3" Wide Stepped Wedge