Table 1.

Grading of evidence

Level 1 ‘We recommend’	Most patients should receive the recommended course of action
Level 2 ‘We suggest’	Different choices will be appropriate for different patients. Each patient needs help to arrive at a management decision consistent with her or his values and preferences
Grade A high quality	Evidence obtained from at least one properly designed randomized controlled trial
Grade B good quality	Evidence obtained from well-designed controlled trials without randomization
Grade C moderate quality	Evidence obtained from well-designed cohort or case-control analytic studies, preferably from more than one center or research group
Grade D poor quality	Evidence obtained from multiple time series with or without the intervention and uncontrolled trials