Strength of recommendation
Grade 1 (strong)
Denoted by the phrase: "We recommend..."
Grade 2 (weak)
Denoted by the phrase: "We suggest..."
Quality of evidence
Level A (high quality)
Source of evidence: Well conducted randomized trials
Level B (moderate quality)
Source of evidence: Less rigorous or inconsistent randomized trials
Level C (low or very low quality)
Source of evidence: Observational studies, case series, and unsystematic observations or expert opinion