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18.3 Appendix 3 - Key to evidence statements and grades of recommendations5

LEVELS OF EVIDENCE
1++ High quality meta-analyses, systematic reviews of randomized controlled trials (RCTs), or RCTs with a

very low risk of bias
1+ Well conducted meta-analyses, systematic reviews, or RCTs with a low risk of bias
1- Meta-analyses, systematic reviews, or RCTs with a high risk of bias
2++ High quality systematic reviews of case control or cohort studies

High quality case control or cohort studies with a very low risk of confounding or bias and a high
probability that the relationship is causal
2+ Well conducted case control or cohort studies with a low risk of confounding or bias and a moderate
probability that the relationship is causal
2- Case control or cohort studies with a high risk of confounding or bias and a significant risk that the
relationship is not causal
3 Non-analytic studies, eg case reports, case series
4 Expert opinion
GRADES OF RECOMMENDATIONS
A At least one meta-analysis, systematic review, or RCT rated as 1++, and directly applicable to the target
population; 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 rates as 2++
D Evidence level 3 or 4; or
Extrapolated evidence from studies rated as 2+
GOOD PRACTICE POINTS
 Recommended best practice based on the clinical experience of the guideline development group

5 http://www.sign.ac.uk/guidelines/fulltext/50/annexoldb.html

 VULVAR CANCER - GUIDELINES 
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