Table 1 Classification of evidence quality and strength of recommendations

A

1

RCTs or meta analyses

B

2

High-quality, repeatable and comprehensive literature reviews, providing evidence synthesis and operability recommendations, or a systematic review

3

Multi-center data comparative studies, multi-center case studies or large sample quantitative studies

C

4

Small sample, single center qualitative or quantitative studies

5

Descriptive studies and/or case reports, usually including observations, warnings and recommendations for managers

D

6

Opinions of authoritative experts or expert committees, generally based on expert experience