Table 2– Quality of evidence and definitions
 Quality of evidence Definition High (⊕⊕⊕⊕) Further research is very unlikely to change our confidence in the estimate of effect Moderate (⊕⊕⊕○) Further research is likely to have an important impact on our confidence in the effect and may change the estimate Low (⊕⊕○○) Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate Very low (⊕○○○) Any estimate of effect is very uncertain