Table 1.

Grades of Recommendation, Assessment, Development and Evaluation system evidence grades

Quality of evidence
A (high quality)	Very confident that the true effect value approximates the effect estimate
B (moderate quality)	There is a moderate degree of confidence in the effect estimates, and it is possible that the true value is close to the estimates, but there is still a possibility that the two are quite different
C (poor quality)	The degree of confidence in the effect estimate is limited and the true value may be quite different from the estimate
D (very low quality)	There is little confidence in the estimates of effects and the true values are likely to be very different from the estimates
Strength of recommendations
Level 1 recommendation (strong)	The benefits clearly outweigh the risks and the credibility of both clinician implementation and population acceptance is high
Level 2 recommendation (weak)	The benefits are equal to the risks, depending on the specific clinical situation. In general, the preferences of doctors and patients play a more important role in the decision-making process