Table 2 Quality of the quality evidence, definitions and underlying methodology

High

Further research is very unlikely to change our confidence in the estimate of effect

RCT or meta-analysis

Moderate

Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate

Downgraded RCTs or upgraded observational studies

Low

Further research is very likely to have an important impact on our confidence in the estimate of effect an its likely to change the estimate

Well-done observational studies with control groups

Very low

Any estimate of effect is very uncertain

Others (e.g., case reports or case series)