Table 2

Criteria for determining evidence level for best evidence synthesis: modified from Lievense et al 30

Level of evidence	Criteria for inclusion in best evidence synthesis
Strong evidence	Generally consistent findings in: Multiple high-quality cohort studies
Moderate evidence	Generally consistent findings in: 1 high-quality cohort study and >2 high-quality case-control studies >3 high-quality case–control studies
Limited evidence	Generally consistent findings in: A single cohort study 1 or 2 case–control studies Multiple cross-sectional studies
Conflicting evidence	Inconsistent findings in <75% of the trials
No evidence	No studies could be found