Stepped wedge randomised controlled trials: systematic review of studies published between 2010 and 2014.
BACKGROUND
In a stepped wedge, cluster randomised trial, clusters receive the intervention at different time points, and the order in which they received it is randomised. Previous systematic reviews of stepped wedge trials have documented a steady rise in their use between 1987 and 2010, which was attributed to the design's perceived logistical and analytical advantages. However, the interventions included in these systematic reviews were often poorly reported and did not adequately describe the analysis and/or methodology used. Since 2010, a number of additional stepped wedge trials have been published. This article aims to update previous systematic reviews, and consider what interventions were tested and the rationale given for using a stepped wedge design.


METHODS
We searched PubMed, PsychINFO, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Web of Science, the Cochrane Library and the Current Controlled Trials Register for articles published between January 2010 and May 2014. We considered stepped wedge randomised controlled trials in all fields of research. We independently extracted data from retrieved articles and reviewed them. Interventions were then coded using the functions specified by the Behaviour Change Wheel, and for behaviour change techniques using a validated taxonomy.


RESULTS
Our review identified 37 stepped wedge trials, reported in 10 articles presenting trial results, one conference abstract, 21 protocol or study design articles and five trial registrations. These were mostly conducted in developed countries (n = 30), and within healthcare organisations (n = 28). A total of 33 of the interventions were educationally based, with the most commonly used behaviour change techniques being 'instruction on how to perform a behaviour' (n = 32) and 'persuasive source' (n = 25). Authors gave a wide range of reasons for the use of the stepped wedge trial design, including ethical considerations, logistical, financial and methodological. The adequacy of reporting varied across studies: many did not provide sufficient detail regarding the methodology or calculation of the required sample size.


CONCLUSIONS
The popularity of stepped wedge trials has increased since 2010, predominantly in high-income countries. However, there is a need for further guidance on their reporting and analysis.
Department of Clinical, Educational and Health Psychology, University College London, 1-19 Torrington Place, London, WC1E 7HB, UK. e.beard@ucl.ac.uk.|Department of Epidemiology and Public Health, University College London, 1-19 Torrington Place, London, WC1E 7HB, UK. e.beard@ucl.ac.uk.
Emma
E
Beard
MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. James.Lewis@lshtm.ac.uk.|Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. James.Lewis@lshtm.ac.uk.
James J
JJ
Lewis
MRC Clinical Trials Unit at University College London, 175 Tottenham Court Road, London, W1T 7NU, UK. a.copas@ucl.ac.uk.
Andrew
A
Copas
Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. calum.davey@lshtm.ac.uk.
Calum
C
Davey
Institute for Global Health, University College London, 30 Guilford Street, London, WC1N 1EH, UK. d.osrin@ucl.ac.uk.
David
D
Osrin
Department of Statistical Science, University College London, 1-19 Torrington Place, London, WC1E 7HB, UK. g.baio@ucl.ac.uk.
Gianluca
G
Baio
MRC Clinical Trials Unit at University College London, 175 Tottenham Court Road, London, W1T 7NU, UK. Jennifer.Thompson@lshtm.ac.uk.|Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. Jennifer.Thompson@lshtm.ac.uk.
Jennifer A
JA
Thompson
MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. Katherine.Fielding@lshtm.ac.uk.
Katherine L
KL
Fielding
Department of Statistical Science, University College London, 1-19 Torrington Place, London, WC1E 7HB, UK. r.omar@ucl.ac.uk.
Rumana Z
RZ
Omar
Department of Obstetrics and Gynaecology, Makerere University College of Health Sciences, P.O. Box 7072, Kampala, Uganda. ononge2006@yahoo.com.
Sam
S
Ononge
Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. James.Hargreaves@lshtm.ac.uk.
James
J
Hargreaves
Institute for Global Health, University College London, 30 Guilford Street, London, WC1N 1EH, UK. audrey.prost@ucl.ac.uk.
Audrey
A
Prost
D006801:Humans; D018579:Patient Selection; D016032:Randomized Controlled Trials as Topic / Q000191:economics / Q000379:methods*; D012107:Research Design; D012109:Research Support as Topic; D018401:Sample Size; D012959:Socioeconomic Factors; D013997:Time Factors