Introduction. It is essential to improve the quality of the evidence in rehabilitation. Multiple publications have highlighted the need to identify whether biases resulting from methodological issues related to rehabilitation characteristics can lead to an overestimation or underestimation of the true rehabilitation intervention effect estimates. This can be achieved using empirical evidence in meta-epidemiological studies. Therefore, this study aimed to synthesise the evidence from studies that addressed the influence of bias domains in randomised controlled trials (RCTs) on rehabilitation intervention effect estimates and discuss how these findings can maximise the trustworthiness of an RCT in rehabilitation.
Methods. We screened studies about the influence of bias on rehabilitation intervention effect estimates published until June 2023. The characteristics and results of the included studies were categorised based on methodological characteristics and summarised narratively, including the effect size estimation (ES) and 95% confidence interval (CI).
Results. We included seven studies with data on 227,806 RCT participants. Our findings showed that rehabilitation intervention effect estimates are likely exaggerated in trials with inadequate/unclear sequence generation and allocation concealment when using continuous outcomes. The influence of blinding was inconsistent, as meta-epidemiological studies showed heterogeneous results, including overestimation, underestimation, or neutral associations for different types of blinding on rehabilitation treatment effect estimates. There was a more consistent pattern when looking at patient-reported outcomes. The impact of attrition bias and intention-to-treat reports inconsistent results. The risk of reporting bias seems to be associated with overestimation of treatment effects.
Conclusion. Bias related to methodological issues can influence rehabilitation treatment effects in different directions. The evidence is mixed and inconclusive due to the poor methodological quality of RCTs and the limited number and quality of studies looking at the influence of bias and treatment effects in rehabilitation. Further studies about the influence of bias in RCTs on rehabilitation intervention effect estimates are needed.
Relevance and importance to patients' statement. The production of more high-quality RCTs can lead to more reliable data and consistent findings. This will support a better clinical decision making to address patients' needs.
No public and/or consumers involvement.