Table 2:

Guideline development using the Grades of Recommendation, Assessment Development and Evaluation Scale (level of evidence) according to study design

Grade	Definition
I	Randomized controlled trials
II-1	Controlled trials without randomization
II-2	Cohort or case-controlled studies
II-3	Multiple time series, dramatic uncontrolled experiments
III	Opinion of respected authorities. Descriptive epidemiology

Notes: Each recommendation was based on quality of the supporting evidence and study design and graded as class-grade: 1 (high), 2-A, 2-B, 2-C (moderate), or 3 (low) quality evidence.