Table 1 Categories for strength of each recommendation

A

Good evidence to support a recommendation for use

B

Moderate evidence to support a recommendation for use

C

Insufficient evidence to support a recommendations for or against use

D

Moderate evidence to support a recommendations against use

E

Good evidence to support a recommendation against use

I

Evidence from at least one properly randomized, controlled trial

II

Evidence from at least one well-designed clinical trial without randomization, from cohort or case-controlled analytic studies, preferably from more than one centre, from multiple time series, or from dramatic results in uncontrolled experiments

III

Evidence from opinions of respected authorities on the basis of clinical experience, descriptive studies, or reports of expert committees