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Table 1 Some reviews of published cluster randomised trials

From: Cluster randomised trials in the medical literature: two bibliometric surveys

Authors Source of trials Years Clustering allowed for in sample size Clustering allowed for in analysis
Donner et al. [8] 16 non-therapeutic intervention trials 1979 – 1989 <20% <50%
Simpson et al. [9] 21 trials from American Journal of Public Health and Preventive Medicine 1990 – 1993 19% 57%
Isaakidis and Ioannidis [11] 51 trials in Sub-Saharan Africa 1973 – 2001 (half post 1995) 20% 37%
Puffer et al. [10] 36 trials in British Medical Journal, Lancet, and New England Journal of Medicine 1997 – 2002 56% 92% a
Eldridge et al. [12] 152 trials in primary health care 1997 – 2000 9% 59%
Varnell et al. [13] 60 trials in American Journal of Public Health and Preventive Medicine 1998 – 2002 20% 54% (all analyses) + 25% (some analyses only)
  1. a My review of trials identified by Puffer et al. [10]