Table 1

Criteria for summary coding of the evidence
Percentages of records supporting association1 Summary code2 Description
0-39% associated 0 Evidence unrelated
40-50% associated in one direction and ≥25% in the opposite 0 Evidence unrelated
40-50% associated in one direction and < 25% in the opposite (+);(−) Possible evidence for a positive/negative relationship
51-100% associated in one direction and ≥25% in the opposite (+);(−) Possible evidence for a positive/negative relationship
51-100% associated in one direction and < 25% in the opposite +; - Convincing evidence for a positive/negative relationship

1 Only valid when relationship was investigated in at least three independent samples, otherwise evidence was regarded "not applicable" (coded N/A).

2 Double signed summary codes are applied when convincing positive “++”, convincing negative “--”, possible positive “(++)”, possible negative “(−−)” or no “00” associations were present in at least four independent samples.

Van Holle et al.

Van Holle et al. BMC Public Health 2012 12:807   doi:10.1186/1471-2458-12-807

Open Data