Table 1.

Level of Evidence and Grade of Recommendations (Adapted from GRADESystem).

Level of evidencea		Confidence in the evidence
High	Data derived from meta-analyses or systematic reviews or from (multiple) randomized trials with high quality.	Further research is unlikely to change our confidence in the estimate of benefit and risk.
Moderate	Data derived from a single randomised controlled trail or multiple non-randomized studies.	Further research (if performed) is likely to have an impact on our confidence in the estimate of benefit and risk and may change the estimate.
Low	Small studies, retrospective observational studies, registries.	Any estimate of effect is uncertain.
Recommendations – Gradeb		Wording associated with the grade of recommendation
Strong		‘must’, ‘‘should’ or ‘‘INASL recommends’
Weak		‘can’, ‘may’ or ‘‘INASL suggests’

^aLevel was graded down if there is a poor quality, strong bias or inconsistency between studies; level was graded up if there is a large effect size.

^bRecommendations were reached by consensus of the panel and included the quality of evidence, presumed patient important outcomes and costs.