Table 12.2.d: Further guidelines for factor 1 (of 5) in a GRADE assessment: Going from assessments of risk of bias to judgements about study limitations for main outcomes

Risk of bias

Across studies

Interpretation

Considerations

GRADE assessment of study limitations

Low risk of bias.

Most information is from studies at low risk of bias.

Plausible bias unlikely to seriously alter the results.

No apparent limitations.

No serious limitations, do not downgrade.

Unclear risk of bias.

Most information is from studies at low or unclear risk of bias.

Plausible bias that raises some doubt about the results.

Potential limitations are unlikely to lower confidence in the estimate of effect.

No serious limitations, do not downgrade.

Potential limitations are likely to lower confidence in the estimate of effect.

Serious limitations, downgrade one level.

High risk of bias.

The proportion of information from studies at high risk of bias is sufficient to affect the interpretation of results.

Plausible bias that seriously weakens confidence in the results.

Crucial limitation for one criterion, or some limitations for multiple criteria, sufficient to lower confidence in the estimate of effect.

Serious limitations, downgrade one level.

Crucial limitation for one or more criteria sufficient to substantially lower confidence in the estimate of effect.

Very serious limitations, downgrade two levels.