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Table 2 Assessment of risk of bias in the studies reviewed

From: Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials

Study Concealment of randomization RCT stopped early Patients blinded Healthcare providers blinded Data collectors blinded Outcome assessors blinded Reporting drop-out or withdrawal Other potential bias Selective outcome reporting Jadad score
Lahti et al. 2013 [22] Yes No Yes Yes Yes No Yes No No 4
Rampelli et al. 2013 [23] Yes No Yes Uncleara Uncleara Uncleara Unclear Yesc Yesc 3
Ferrario et al. 2014 [27] Yes No Yes Uncleara Uncleara Uncleara Yes No No 3
Bjerg et al. 2015 [19] Yes No Yes Yes Yes Yes Yes Yesb No 5
Brahe et al. 2015 [20] Yes No Yes No No No Yes No No 4
Hanifi et al. 2015 [21] Yes No Yes Yes Yes Yes Yes Yesb No 5
Simon et al. 2015 [24] Yes No Yes Uncleara Uncleara Uncleara Yes No No 4
  1. Based on PRISMA (and Cochrane)’s tools for assessing risk of bias. The Jadad score is a three-item instrument that evaluates likelihood of bias in terms of quality of randomization, quality of blinding, and reasons for withdrawal/drop-out. It is compiled of the following quality items from the table: Concealment of randomization, Patients blinded, Healthcare providers blinded, Data collectors blinded, Outcome assessors blinded, and Reporting drop-out or withdrawal
  2. aDouble-blinded study but unclear whether healthcare providers, data collectors, and outcome assessors were all blinded
  3. bPerformed next-generation sequencing on fecal samples from a subgroup of the included individuals. Bjerg et al. selected 10 (of 32) placebo-treated and 10 (of 32) probiotic-treated participants with the highest triacylglycerol concentration in the blood at week 0. Hanifi et al. selected 20 (all) placebo-treated and 17 (of 20) probiotic-treated participants from the group with the highest dose (10 × 109 colony-forming units) of the probiotic treatment
  4. cNo direct comparison between treatment groups was made for the age-related dysbiosis