This short introduction to the SW-CRT introduces the design and considers some settings where it may be particularly useful.

1. Reconciling Scientific Rigour with
the Service Imperative
30/08/2016
Society for Clinical Trials Conference
Arlington, VA
May 17th 2015
Professor Richard Lilford

2. Collaborations for Leadership in
Applied Health Research Care
Hospital
Primary Care
Local Authority
Intervention
Development
Evaluation
£20m £10m

4. Step Wedge Design
• What?
• Why?
Today’s talk: trialsCluster

5. What is a Step Wedge Design?
Hemming, Lilford & Girling. Stat Med. 2015; 34(2): 181-96.
Cluster exposed to intervention
Cluster unexposed to intervention (control)
Time
1
2
3
4
5
6
Cluster
Many variations on a theme

6. What is the Counter-factual?
Two Types of Cluster Study:
Cross-sectional
Cohort

7. Why Consider a SWD, rather than
Parallel Cluster Trial?
1. Ethics
2. Acceptability
3. Logistics
• Sample size
• Interaction between
intervention effect and time
Co-exist
4. Scientific Reasons

8. Disadvantages of SWDs?
Always
Analytically
complex
Sometimes
Violation of
sequence
Increase trial
duration
Long gap
between
intervention &
outcome
Spurious
All cluster
studies

9. Step Wedge Trials vs.
Step Wedge Studies
Time
Cluster
1
2
3
4
5
6
7
8
But may be “instrumental variable”
Naturalistic SWD
= Instrumental variable approach

10. The End