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. 2022 Jan 14;61(4):2091–2101. doi: 10.1007/s00394-021-02789-5

Table 3.

Grading the overall certainty of evidence according to methodological quality, outcome-specific certainty of evidence, biological plausibility and consistency of results, and definition of the overall certainty of evidence in a modified form according to the GRADE approach [11]

Overall certainty of evidence Underlying criteria Definition/Explanation
Convincing

• At least one SR with or without MA of prospective studies available

• If more than one SR with or without MA are available: all overall results must be consistent.a

• In case of a positive or negative association, biological plausibility is given

• All included SRs with or without MA must reach at least a “moderate” outcome-specific certainty of evidenceb; in addition all included SRs must reach at least a methodological qualityc of “moderate”

 There is high level of confidence that the true effect lies close to that of the estimate(s) of the effect
Probable

• At least one SR with or without MA of prospective studies available

• If more than one SR with or without MA are available, the majority of overall results must be consistent.a

• In case of a positive or negative association, biological plausibility is given

• The majorityd of included SRs with or without MA must have reached at least a “moderate” certainty of evidenceb; in addition all included SRs must reach at least a methodological qualityc of “moderate”

There is moderate confidence in the effect estimate(s):

The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different
Possible

• At least one SR with or without MA of prospective studies available

• If more than one SR with or without MA are available, the majority of overall results must be consistent.a

• In case of a positive or negative association, biological plausibility is given

• The majorityd of included SRs with or without MA must reach at least a “low” certainty of evidenceb; in addition the majorityd of all included SRs must reach at least a methodological qualityc of “moderate”

Confidence in the effect estimate(s) is limited:

The true effect may be substantially different from the estimate of the effect
Insufficient

• No SR is available

OR

• The majorityd of included SRs with or without MA reach a “very low” certainty of evidenceb; in addition the majority of all included SRs reach a methodological qualityc of “low”

There is very little confidence in the effect estimate (s):

The true effect is likely to be substantially different from the estimate of effect

MA meta-analysis, SR systematic review

aConsistent = overall results of the SR have to be consistently either risk reducing or risk elevating or consistently showing no risk association

bOutcome-specific certainty of evidence refers to the NutriGrade rating

cMethodological quality refers to the AMSTAR 2 rating; SRs rated as “critically low” by AMSTAR 2 are not considered

dMajority: > 50% of the included SRs