Reporting bias assessment; involves identification whether studies in the systematic review have selective reporting of outcomes, which could lead to overestimation or underestimation of the true effect size.

Reporting bias Assessment can be performed using the following methods:

1. Checking for discrepancies between the study protocol and the published report.

2. Checking if all relevant outcomes are reported, and if not, whether the purpose for not reporting them is justified.

3. Comparing the results (findings) of the study with the results reported in conference abstracts or previous versions of the manuscript.

Certainty evidence; Entails the process of evaluating the quality of the evidence from each study and the confidence in the overall body of evidence.

It can be performed by using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) framework for certainty evidence. The GRADE framework assesses the quality of evidence by considering four domains such as study design, risk of bias, consistency of results, and directness of evidence. To perform GRADE assessment, first classify the quality of evidence for each outcome based on the study design and then adjust it based on the risk of bias, consistency of results, and directness of evidence. You can then rate the quality of evidence as high, moderate, low, or very low based on the adjusted score.

You might want to use some of the available tools for this assessment. A good example is the Critical Appraisal Skills Program (CASP) tool.

A risk of bias assessment is done to improve the transparency of the evidence synthesis findings. Each study included in the evidence synthesis (systematic review/meta-analysis) is assessed for the possibility of bias either in the design, conduct or analysis of the study. It is done with the help of critical appraisal tools. Numerous critical appraisal tools are available for various study designs.

Some of the available tools:

• RCTs: Cochrane’s Risk of bias 2 (RoB 2) tool, Jadad scale

• Non-randomized trials: Risk of bias in Non-randomized Studies of Interventions (ROBINS-I tool)

• Observational (case-control/cohort studies): Newcastle Ottawa Scale, JBI Checklist for Case-control/Cohort studies

• Cross-sectional studies: Newcastle Ottawa scale adapted for cross-sectional study, AXIS tool, JBI Checklist for Prevalence Study

We should be cautious in choosing the right tool for the right design and make sure that it is the latest version of the tool.

For example, Cochrane’s Risk of bias 2 (RoB 2) tool for RCTs has 25 questions divided into five domains.

Based on the response to 25 questions, each study will be classified into one of the three categories: low risk of bias, some concerns and high risk of bias.

This will tell us the quality of each study included in the evidence synthesis.

Thank you for your responses Joel Wanzala Bonniface Oryokot and Dhanajayan Govindan