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Table 2 Cochrane Collaboration tool for assessing risk of bias

From: Strategies for increasing participation in mail-out colorectal cancer screening programs: a systematic review and meta-analysis

First author and year Random sequence generation Allocation concealment Blinding of participants and personal Blinding of outcome assessment Incomplete outcome data Selective reporting Other bias Overall Risk of Bias
Benton et al. [16] H H H L L L L H
Cole et al. [17] L L U L L L L L
Cole et al. [18] L L L L L L L L
Cole et al. [19] U U U L U L U U
Corondado et al. [20] L U U L L L L L#
Denters et al. [21] L L U U L U U U
Deutekom et al. [22] L L L U L L L L
Gupta et al. [23] L L L L L L L L
Hewitson et al. [24] L L L L L L L L
Hirst et al. [25] L L L L L U L L
Hughes et al. [26] H H U U H U H H
King et al. [27] U U U L L U H H
King et al. [28] U U U L L U L U
Libby et al. [29] L L L L U L L L
Lo et al. [30] L U U L L U L U
McGregor et al. [31] U L L L L L L L
Moss et al. [32] L L U L L L L L
Myers et al. [33] U U L L U L L U
Neter et al. [34] L L U L L L L L
O'Carroll et al. [35] L L U L L L L L
Robinson et al. [36] U U U L L U L U
Santare et al. [37] L L U U L U L U
van Roon, [38] L L U L U U L U
van Rossum et al. [39] L L L U L L L L
Verne et al. [40] U U L U L U U U^
Wardle et al. [41] (1) L L L L L L L L
Wardle et al. [41] (2) L L L L L L L L
Wardle et al. [41] (3) L L L L L L L L
Wardle et al. [41] (4) L L L L L U U L
Watson et al. [42] L U U L L L L L
White et al. [43] U U U L L L L U*
Zajac et al. [44] L L L U L L H H¥
Zubero et al. [45] L L L L L U L L
  1. L = low, U = unclear, H = high
  2. #Risk of bias is high for the email intervention as not randomly assigned
  3. ^Risk of bias is suggested to be high for the self- versus lab-analyzed stool sample intervention as it is much less likely that participants would return self-analyzed negative results
  4. *Risk of bias is suggested to be high for the outdoor advertising intervention implemented in White et al. 2015 because participants not randomly allocated
  5. ¥Zajac et al., 2010 reports on the same sample as Cole et al., 2007 and was therefore deemed high risk of bias