Part 2: An overview of RoB 2

Summary

This transcript outlines the process of conducting a risk of bias (ROB) assessment for systematic reviews. It details how each outcome is evaluated through a set of signaling questions to assess potential biases at various stages of a study, such as randomization, intervention implementation, and outcome measurement. The process aims to integrate these bias assessments into results, allowing for stratified meta-analyses and a more transparent understanding of trial findings. Special considerations for cluster and crossover trials are also discussed, along with the goal of improving how risk of bias is reflected in review conclusions.

Takeaways

• 😀 The process of risk of bias assessment involves evaluating each outcome in a study and making judgments based on various domains like randomization, implementation, and measurement.
• 😀 Signaling questions are used to increase transparency in the risk of bias process by prompting yes/no responses, which are then used to map the risk of bias for each domain.
• 😀 Bias can be introduced at various stages of a randomized trial, including during randomization, implementation of the intervention, measurement of outcomes, and reporting of results.
• 😀 An important goal of ROB2 (Risk of Bias 2) is to integrate risk of bias judgments into the meta-analysis results, allowing for stratification of results based on risk of bias.
• 😀 Randomized trials are designed to minimize bias, but biases can still arise, and risk of bias tools assess areas where these biases can impact outcomes.
• 😀 The effect of interest in trials can be either the effect of assignment to the intervention (intention-to-treat analysis) or the effect of adhering to the intervention (per-protocol effect).
• 😀 Review authors answer signaling questions that are either yes, probably yes, probably no, no, or no information, which are used to guide overall risk of bias judgments.
• 😀 In the signaling process, answers like 'probably yes' and 'yes' suggest a lower risk of bias, while 'probably no' and 'no' suggest a higher risk of bias, with 'no information' having context-specific implications.
• 😀 The risk of bias judgment is determined by the worst assessment across all domains, meaning that a result can only be considered at low risk of bias if it is deemed low risk for every domain.
• 😀 Special adaptations to the risk of bias tool address issues in cluster randomized trials and crossover trials, ensuring that unique design elements are accounted for.
• 😀 In future systematic reviews, it is hoped that the risk of bias assessments will be integrated into the analysis, with forest plots stratified by risk of bias and analyses restricted to studies at low risk of bias.

Q & A

What is the first step in the process of conducting a risk of bias assessment for a study?

The first step is to specify the result being assessed, taking into account that sometimes multiple results are reported for the same outcome domain.

What are the sources of information that may be used to inform the risk of bias assessment?

The sources of information include study protocols, clinical report forms, and other relevant documentation that provide insight into the study design and execution.

How does the risk of bias assessment process integrate with the results of a meta-analysis?

The risk of bias judgments are integrated into the results and conclusions of a systematic review, allowing for the stratification of the meta-analysis based on the overall risk of bias, such as focusing on studies with low risk of bias.

What is the purpose of conducting an intention-to-treat analysis in randomized trials?

The intention-to-treat analysis compares all participants who were assigned to the intervention with all those who were not, regardless of whether they adhered to the intervention, to reflect real-world conditions and ensure unbiased results.

What does 'adhering to intervention' mean in the context of randomized trials?

Adhering to intervention refers to participants following the intervention as prescribed in the trial protocol, and in some cases, researchers may be interested in the effect of adhering to the intervention, which is referred to as the per-protocol effect.

How are signaling questions used in the risk of bias assessment?

Signaling questions guide the assessment of risk of bias by prompting review authors to answer with 'yes,' 'probably yes,' 'probably no,' 'no,' or 'no information,' and these answers are mapped to risk of bias judgments, which help in determining the overall risk for each domain.

What is the overall risk of bias judgment based on in the ROB2 tool?

The overall risk of bias judgment is based on the worst judgment for any individual domain. If any domain is rated as high risk of bias, the overall result is considered high risk of bias.

What is the importance of baseline differences between intervention groups in randomized trials?

Baseline differences between intervention groups can indicate a potential issue with the randomization process, which may lead to bias. This is assessed in the risk of bias domain for randomization.

How are cluster randomized trials different from individually randomized trials in terms of risk of bias assessment?

Cluster randomized trials have additional considerations such as bias arising from the timing of participant identification and recruitment, missing outcome data for entire clusters, and potential lack of awareness of the trial by outcome assessors.

What are the potential biases addressed in the adapted ROB2 tool for crossover trials?

The adapted ROB2 tool for crossover trials addresses biases such as carryover effects (where the effects of the first intervention may influence the second) and selective reporting of first-period data as if it were from a parallel trial.