Abstract
BackgroundBias in randomized controlled trials (RCTs) can lead to underestimation or overestimation of the true effects of interventions. Surgical RCTs may suffer from the risk of bias (RoB) that is avoidable in trials of other interventions, and vice versa. We aimed to compare the adequacy of RoB assessments in surgical versus non-surgical RCTs included in Cochrane reviews and to assess the most common differences in those RoB assessments. Due to specificities of surgical trials, i.e. difficulties associated with blinding of surgical interventions, we hypothesized that assessments of surgical trials may be more adequate, compared to RCTs of non-surgical interventions.MethodsThis was a methodological study, analyzing methods of published Cochrane systematic reviews. Data were extracted from RoB tables in Cochrane reviews (judgments and accompanying explanatory comment) for the following four RoB domains used in the 2011 Cochrane RoB tool: randomization, allocation concealment, blinding of participants and personnel, and blinding of outcome assessors. We defined adequate assessments as those that were in line with instructions from the Cochrane Handbook for Systematic Reviews of Interventions. The prevalence of adequate assessments was compared in surgical versus non-surgical trials. The most common differences in both groups of reviews were presented.ResultsIn 729 analyzed Cochrane reviews, there were 10,537 included trials. The prevalence of adequate RoB judgments made by Cochrane authors ranged from 87.9, 95%CI (87.3 to 88.6%) for randomization to 70.7, 95%CI (69.8 to 71.5%) for blinding of participants and personnel. For all analyzed RoB domains, the prevalence of adequate RoB domains was higher in surgical trials than in non-surgical trials. For two RoB domains assessing blinding, this difference between surgical and non-surgical trials was statistically significant (P < 0.001), while the difference was not significant for the RoB domain regarding randomization (P = 0.124) and allocation concealment (P = 0.039, β < 0.8).ConclusionsRoB judgments were more in line with instructions from the Cochrane Handbook when Cochrane reviews assessed surgical trials, compared to those that analyzed non-surgical interventions. However, further steps are warranted to scrutinize RoB assessment in trials of both surgical and non-surgical interventions.
Highlights
Bias in randomized controlled trials (RCTs) can lead to underestimation or overestimation of the true effects of interventions
risk of bias (RoB) assessments made by authors of published systematic reviews should not be taken at the face value, as we have shown in multiple studies that RoB assessments in many Cochrane reviews were inadequate and inconsistent [7,8,9,10,11,12,13,14]
The aim of this study was to compare the adequacy of RoB assessments in surgical versus non-surgical RCTs included in Cochrane reviews and to assess the most common inadequate judgments in those RoB assessments
Summary
Bias in randomized controlled trials (RCTs) can lead to underestimation or overestimation of the true effects of interventions. Randomized controlled trials (RCTs) are crucial for assessing the effects of interventions, but various types of bias in RCTs can lead to underestimation or overestimation of the true effects of interventions [1, 2]. It has been reported that few RCTs in a certain surgical field have low RoB [4, 5]. Gurusamy et al suggested that it is possible to conduct RCTs in the field of surgery with low RoB and that better understanding of RoB may result in better trials, with a better estimate of the true effects of interventions [6]
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