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Table 1 Review: study characteristics

From: Approaches to multiplicity in publicly funded pragmatic randomised controlled trials: a survey of clinical trials units and a rapid review of published trials

Characteristic   n/N %
Journal Annals of Internal Medicine 4/138 3%
BMJ 11/138 8%
JAMA 28/138 20%
Lancet 30/138 22%
NEJM 36/138 26%
NIHR HTA journal library 17/138 12%
PlosMED 12/138 9%
Trial designa Parallel group: 2 treatment groups 94/138 68%
Parallel group: > 2 treatment groups 18/138 13%
Cluster randomised 23/138 17%
Crossover 2/138 1%
Factorial 5/138 4%
Stepped wedge 2/138 1%
Non-inferiority 18/138 13%
Equivalence 1/138 1%
Total number of randomised participants - median (IQR) 574 (312, 2043)
MULTIPLICITY
Primary outcomeb More than one outcome stated 21/138 15%
Two outcomes 17  
Three outcomes 4  
More than one comparison made 28/138 20%
Two comparisons 16  
Three comparisons 4  
Four comparisons 2  
Five comparisons 1  
>Five comparisons (maximum 20) 5  
Secondary outcome More than one outcome stated 134/138 97%
Median (IQR) outcomes stated 8 (5, 13)  
More than one comparison made 132/138 96%
Median (IQR) comparisons made 14.5 (7, 26)  
More than two treatment groupsc 23/138 17%
Number of treatment comparisons made Oned 1  
Two 13  
Three 6  
Four 1  
Five 1  
Eight 1  
Any subgroup analyses performed 85/138 62%
  Median (IQR) subgroup analyses 4 (2, 7)  
Any interim analyses performed 38/135 28%
  One 22  
  Two 9  
  Three 3  
  Four 3  
  Five 1  
  1. Notes: a Trials could be classified in more than one design category, e.g. a cluster randomised, factorial, non-inferiority trial.
  2. bDiscrepancies between the numbers of outcomes stated and comparisons made were either due to multiple time points being analysed or multiple analysis approaches taken, with none stated as primary.
  3. cThis includes parallel group trials with > 2 treatment groups and factorial trials.
  4. dIn this trial one treatment arm was dropped due to futility at an interim analysis, so the final analysis comprised just two treatment groups and therefore one comparison.
  5. Abbreviations: BMJ British Medical Journal, IQR interquartile range, JAMA Journal of the American Medical Association, NEJM New England Journal of Medicine, NIHR HTA National Institute of Health Research Health Technology Assessment, PlosMED Public Library of Science Medicine