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Table 3 Characteristics of included Cochrane and non-Cochrane reviews—evaluation of the Cochrane tool for assessing risk of bias in randomized clinical trials

From: Evaluation of the Cochrane tool for assessing risk of bias in randomized clinical trials: overview of published comments and analysis of user practice in Cochrane and non-Cochrane reviews

Publication characteristics 100 Cochrane reviews (100 %) 100 non-Cochrane reviews (100 %) P value*
Intervention    
 Pharmacologic 55 (55 %) 29 (29 %) 0.020
 Non-pharmacologic 45 (45 %) 71 (71 %) 0.061
Review has ≥1 meta-analysis    
 Yes 85 (85 %) 45 (45 %) 0.0065
Included trials    
 Number of randomized clinical trials in total 1242 1249  
  -Lowa risk of bias 74 (6 %) 25 of 424e (6 %) 1.00
  -Unclearb risk of bias 407 (33 %) 226 of 424e (53 %) 0.0001
  -Highc risk of bias 761 (61 %) 173 of 424e (41 %) 0.0001
 Reviews with ≥1 low risk of bias trial and ≥1 high risk of bias trial 26 (26 %) 6 of 18f (33 %) 0.60
 Reviews with ≥1 low risk of bias trial and ≥1 high or unclear risk of bias trial 32 (32 %) 8 of 18f (44 %) 0.47
 Number of randomized clinical trials includedd in a review    
  -One to five 39 (39 %) 38 (38 %) 1.00
  -Six to ten 23 (23 %) 26 (26 %) 0.75
  ->Ten 38 (38 %) 36 (36 %) 0.89
  1. *P values were calculated with Fisher’s two-tailed exact test
  2. aIf a trial had all standard domains (not including the “other bias” domain) judged as “low” risk of bias, we defined the trial as “low risk of bias”
  3. bIf a trial had at least one of the standard domains (not including the “other bias” domain) judged as “unclear” risk of bias and no domains judged as “high” risk of bias, we defined the trial as “unclear risk of bias.” The judgement of at least one standard risk of bias domain (not including the “other bias” domain) as “unclear” was found in 1103 of 1242 included randomized clinical trials (89 %)
  4. cIf a trial had at least one of the six standard domains (not including the “other bias” domain) judged as “high” risk of bias, we defined the trial as “high risk of bias”
  5. dWe only included systematic reviews with one or more randomized clinical trials included in their analyses
  6. eIt was only possible to assess whether a trial was judged as “low,” “unclear” or “high” risk of bias in 18 non-Cochrane reviews (which provided information on risk of bias judgements for all six standard domains (not including the “other bias” domain) for individual trials via a “risk of bias graph/summary” or “characteristics of studies” section)
  7. fThe 18 non-Cochrane reviews included 424 randomized clinical trials in total