Strength of a recommendation
Strong
Benefits > Risks
Risks > Benefits
Weak
Benefits ~ Risks
Quality of evidence precludes accurate assessment of risks and benefits
Grading quality of evidence
High
Additional research is considered very unlikely to change confidence in the estimate of effect
Moderate
Further research is likely to have an important impact on in the estimate of effect
Low
Further research is very likely to change the estimate of the effect

Adapted from Guyatt G, Gutterman D, Baumann MH, Addrizzo-Harris D, Hylek EM, Phillips B, et al. Grading strength of recommendations and quality of evidence in clinical guidelines. Chest 2006;129:174-81.