Table 3 Evidence grades (based on the previous guideline version [1])

A Randomized, double-blind clinical trial of high quality (for example, sample-size calculation, flow chart of patient inclusion, intention-to-treat (ITT) analysis, sufficient sample size)

B Randomized clinical trial of lesser quality (for example, only single-blind, limited sample size: at least 15 patients per study arm)

C Comparative trial with severe methodological limitations (for example, not blinded, very small sample size, no randomization) or large retrospective observational studies.

D Adapted from existing consensus document or statement based on expert opinion voting during consensus conference