Table 1

Evidence level of systematic reviews
Score Source of evidence
1++ High quality meta analyses or systematic reviews of RCT’s
1+ Well conducted meta analyses or systematic reviews of RCT’s
1- Meta analyses or systematic reviews of RCT’s
2++ High quality systematic reviews of case control or cohort studies
2+ Well conducted case control or cohort studies with low risk of bias
2- Case control or cohort studies with high risk of bias
3 Case reports or case series
4 Expert opinion or formal consensus

From Scottish Intercollegiate Guidelines Network [13].

McNeill et al.

McNeill et al. BMC Public Health 2012 12:955   doi:10.1186/1471-2458-12-955

Open Data