TY - JOUR
T1 - Bias in recruitment to cluster randomized trials
T2 - a review of recent publications
AU - Brierley, Gwen
AU - Brabyn, Sally Elizabeth
AU - Torgerson, David
AU - Watson, Judith
N1 - © 2011 Blackwell Publishing Ltd.
PY - 2011/8
Y1 - 2011/8
N2 - Objectives To assess recruitment bias and the techniques employed to counter this problem in a recent selection of published cluster randomized trials. Design Review of 24 cluster trials published in 2008 in four leading medical journals. Data extraction Studies were assessed by four reviewers to identify if an alternative design could have been employed using individual randomization. Data were also extracted on the randomization procedure and the likelihood of this introducing bias to the selection of participants into the study. Results Of the 24 trials, eight could have used individual randomization as an alternative to cluster allocation. Seven studies could have recruited participants prior to cluster randomization but did not. In eight studies where recruitment bias was possible, more than half (five) demonstrated some evidence of differential recruitment rates. Conclusions Many cluster trials published in leading medical journals are not clear in their justification for the design. We also found significant proportions of cluster trials used suboptimal designs that increase their risk of introducing selection bias. Better design of cluster trials is possible and should be adopted.
AB - Objectives To assess recruitment bias and the techniques employed to counter this problem in a recent selection of published cluster randomized trials. Design Review of 24 cluster trials published in 2008 in four leading medical journals. Data extraction Studies were assessed by four reviewers to identify if an alternative design could have been employed using individual randomization. Data were also extracted on the randomization procedure and the likelihood of this introducing bias to the selection of participants into the study. Results Of the 24 trials, eight could have used individual randomization as an alternative to cluster allocation. Seven studies could have recruited participants prior to cluster randomization but did not. In eight studies where recruitment bias was possible, more than half (five) demonstrated some evidence of differential recruitment rates. Conclusions Many cluster trials published in leading medical journals are not clear in their justification for the design. We also found significant proportions of cluster trials used suboptimal designs that increase their risk of introducing selection bias. Better design of cluster trials is possible and should be adopted.
UR - http://www.scopus.com/inward/record.url?scp=84857046818&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2753.2011.01700.x
DO - 10.1111/j.1365-2753.2011.01700.x
M3 - Article
C2 - 21689213
SN - 1356-1294
VL - 18
SP - 878
EP - 886
JO - Journal of Evaluation in Clinical Practice
JF - Journal of Evaluation in Clinical Practice
IS - 4
ER -