Table 2

Quality of evidence and definitions

High qualityFurther research is very unlikely to change the confidence in the estimate of effects
Moderate qualityFurther research is likely to have an important impact on the confidence in the estimate of effect and may change the estimate
Low qualityFurther research is very likely to have an important impact on the confidence in the effect and is likely to change the estimate
Very low qualityAny estimate of the effect is very uncertain