level I study directly on the topic supports the recommendation.
B
Moderate
A preponderance of level II studies, but at least 1 level II study directly on the topic supports the recommendation.
C
Weak
A single level II study at <25% critical appraisal scores or a preponderance of level III and IV studies, including consensus statements by content experts support the recommendation.
D
Theoretical/
Foundational
A preponderance of evidence from animal or cadaver studies, from conceptual/theoretical models/principles, or from basic science/bench research, or published expert opinion in peer-reviewed journals supports the recommendation.
P
Best practice
Recommended practice based on current clinical practice norms, exceptional situations where validating studies have not or cannot be performed, and there is a clear benefit, harm or cost, and/or the clinical experience of the guideline development group.
R
Research
An absence of research on the topic, or conclusions from higher-quality studies on the topic are in disagreement. The recommendation is based on these conflicting conclusions or absent studies.
