Table 5.

Levels of evidence, grades of recommendation and good practice points

Levels of evidence
1	1++ high-quality meta-analyses, systematic reviews of RCTs, or RCTs with a very low risk of bias
	1+ well-conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias
	1– Meta-analyses, systematic reviews of RCTs, or RCTs with a high risk of bias
2	2++ high-quality systematic reviews of case-control or cohort or studies
	2+ high-quality case-control or cohort studies with a very low risk of confounding, bias, or chance and a high probability that the relationship is casual
	2– well-conducted case control or cohort studies with a low risk of confounding, bias, or chance and a moderate probability that the relationship is casual
3	non-analytic studies, e.g. case reports, case series
4	expert opinion
Grades of recommendation
A	at least one meta-analysis, systematic review, or RCT rated as 1++, and directly applicable to the target population; or a systematic review of RCTs or a body of evidence consisting principally of studies rated as 1+, directly applicable to the target population, and demonstrating overall consistency of results
B	a body of evidence including studies rated as 2++, directly applicable to the target population, and demonstrating overall consistency of results; or extrapolated evidence from studies rated as 1++, or 1+
C	a body of evidence including studies rated as 2+, directly applicable to the target population, and demonstrating overall consistency of results; or Extrapolated evidence from studies rated as 2++
D	evidence level 3 or 4; or extrapolated evidence from studies rated as 2+
Good practice points
RBP	recommended best practice based on the clinical experience of the guideline development group