Level of evidence Criteria Level 1 Randomised controlled trials without important limitations Level 2 Randomised controlled trials with important limitations Observational studies with overwhelming evidence Level 3 Other observational studies Level 4 Inadequate or no data in population of interest Anecdotal evidence or clinical experience
Level of evidence Criteria Level 1 Randomised controlled trials without important limitations Level 2 Randomised controlled trials with important limitations Observational studies with overwhelming evidence Level 3 Other observational studies Level 4 Inadequate or no data in population of interest Anecdotal evidence or clinical experience