Table 3.
Characteristics of included Cochrane and non-Cochrane reviews—evaluation of the Cochrane tool for assessing risk of bias in randomized clinical trials
| 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 |
*P values were calculated with Fisher’s two-tailed exact test
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”
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 %)
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”
dWe only included systematic reviews with one or more randomized clinical trials included in their analyses
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)
fThe 18 non-Cochrane reviews included 424 randomized clinical trials in total