Original Article
Copyright ©2011 Baishideng Publishing Group Co.
World J Gastroenterol. Aug 14, 2011; 17(30): 3479-3486
Published online Aug 14, 2011. doi: 10.3748/wjg.v17.i30.3479
Table 1 Levels of evidence and strength of recommendation
Levels of evidence
1Randomized clinical trials and/or meta-analyses
2Single randomized clinical trail
3Prospective observational studies
4Retrospective studies
5Cross-sectional surveys and descriptive studies
6Opinion of experts in guidelines or consensus
Strength of recommendations
AStrong (levels of evidence 1 and 2)
BRelatively strong (levels of evidence 3, 4 and 5)
CWeak (level of evidence 6)