Article type
Year
Abstract
Background: There is some controversy whether risk of bias (RoB) may threaten the internal validity of a clinical trial by distorting the magnitude of treatment effect estimates. In dentistry, no study to date has attempted to evaluate the influence of RoB on clinical outcomes.
Objective: The aim of this study was to assess the effect of RoB on the size of treatment effect estimates in randomized controlled trials (RCTs) in two dental specialties, periodontology and implant dentistry.
Methods: The Cochrane Database of Systematic Reviews (CDSR) was searched for systematic reviews (SRs) including meta-analyses of RCTs of interventions in periodontology and implant dentistry. Cochrane SRs were selected because they normally provide homogenous assessment of RoB. The search was performed in September 2014. Random-effect meta-analyses were performed by grouping RCTs with different RoBs in three domains (sequence generation, allocation concealment, and blinding of outcome assessment). Only SRs including 10 or more RCTs in the meta-analyses were included. This procedure was used to increase power and precision. The association between RoB characteristics and the magnitudes of intervention effects in the meta-analyses was investigated by the use of meta-regression analysis.
Results: Three SRs (two from periodontology field) included at least 10 RCTs in the meta-analyses, and overall they generated information about the conduct of 27 meta-analyses. No significant differences in the relationship of the RoB level with the size of treatment effect estimates were found, although a trend for exaggerated estimates was observed in domains with unclear RoBs.
Conclusions: Several confounders might have influenced the strength of the association between size of treatment effect estimates and different levels of RoB. Researchers should seek to reduce the RoB adequately in domains that may potentially threaten the internal validity of the trial.
Objective: The aim of this study was to assess the effect of RoB on the size of treatment effect estimates in randomized controlled trials (RCTs) in two dental specialties, periodontology and implant dentistry.
Methods: The Cochrane Database of Systematic Reviews (CDSR) was searched for systematic reviews (SRs) including meta-analyses of RCTs of interventions in periodontology and implant dentistry. Cochrane SRs were selected because they normally provide homogenous assessment of RoB. The search was performed in September 2014. Random-effect meta-analyses were performed by grouping RCTs with different RoBs in three domains (sequence generation, allocation concealment, and blinding of outcome assessment). Only SRs including 10 or more RCTs in the meta-analyses were included. This procedure was used to increase power and precision. The association between RoB characteristics and the magnitudes of intervention effects in the meta-analyses was investigated by the use of meta-regression analysis.
Results: Three SRs (two from periodontology field) included at least 10 RCTs in the meta-analyses, and overall they generated information about the conduct of 27 meta-analyses. No significant differences in the relationship of the RoB level with the size of treatment effect estimates were found, although a trend for exaggerated estimates was observed in domains with unclear RoBs.
Conclusions: Several confounders might have influenced the strength of the association between size of treatment effect estimates and different levels of RoB. Researchers should seek to reduce the RoB adequately in domains that may potentially threaten the internal validity of the trial.