Table 1. Level of evidence.

Class	Explanation
High	At least 1 RCT or SR/meta-analysis with no concerns of study quality
Moderate	At least 1 RCT or SR/meta-analysis with minor concerns of study quality or at least 1 cohort/case-control/diagnostic test design study with no concerns of study quality
Low	At least 1 cohort/case-control/diagnostic test study with minor concerns of study quality or at least 1 single arm before-after study, cross-sectional study with no concerns of study quality
Very low	At least 1 cohort/case-control/diagnostic test design study with serious concerns of study quality or at least 1 single arm before-after study, cross-sectional study with minor/severe concerns of study quality

RCT = randomized controlled trial; SR = systematic review.