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Systematic Reviews: How-To in Detail

Why Assess for Bias and Quality?

Conducting risk of bias assessment, sometimes called quality assessment, is a defining feature of the systematic review process that  elevates the methodological rigor and transparency of reported results. To do so, you will need a tool that fits the study designs included in your systematic review and establish a method to conduct the assessment in a dual-blind manner.

Tools for Assessing Risk of Bias and Quality


Common risk of bias tools:

Levels of Evidence


GRADE and Confidence Assessment
The recent PRISMA 2020 reporting guidelines now request an assessment of the certainty of the evidence. This can be tied into risk of bias through some tools, such as GRADE.


Confidence in the effect estimate

The 4 levels of Certainty in effect estimates / Quality of evidence

  • High: We are very confident in the evidence supporting the recommendation.
    • Further research is very unlikely to change the estimates of effect.
  • Moderate: We are moderately confident in the evidence supporting the recommendation.
    • Further research could have an important impact,which may change the estimates of effect.
  • Low: We have only low confidence in the evidence supporting the recommendation.
    • Further research is very likely to have an important impact, which is likely to change the estimate of effect.
  • Very low: Any estimate of effect is very uncertain.


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