Table 2

Criteria for ascertainment of evidence level for best-evidence synthesis, adapted from Lievense et al[15,16]
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:
    One high-quality cohort study and >2 high quality case-control studies
Limited evidence Generally consistent findings in:
    Single cohort study
    One or two case-control studies or
    Multiple cross-sectional studies
Conflicting evidence Inconsistent findings in <75% of the trials
No evidence No studies could be found

Quirk et al.

Quirk et al. BMC Psychiatry 2013 13:175   doi:10.1186/1471-244X-13-175

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