Table 1.

Level of Evidence Scale

Level of Evidence	Study Type
1a	Systematic reviews and meta-analyses that include more than one (well-designed) randomized controlled trial (RCT)
1b	(Well-designed) RCT
2	(Well-designed) controlled studies, without randomisation, ie quasi-experiments; or pilot RCTs (self-designated)
3	(Well-designed) case-control or cohort studies, (preferably from more than one centre or research group)
4	Findings obtained from descriptive, other observational and/or qualitative research designs (including case studies), cross-sectional studies, user studies