Table 1

Definitions of Levels and Grades for Recommendations13

Quality IndicatorType of Evidence
Level of evidence
 IEvidence from at least one properly randomized, controlled trial
 IIEvidence from at least one well-designed clinical trial, without randomization; from cohort or case-controlled analytic studies (preferably from more than one center); from multiple time series; or from dramatic results from uncontrolled experiments
 IIIEvidence from opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees
Grade of recommendation
 AGood evidence to support a recommendation for use
 BModerate evidence to support a recommendation for use
 CPoor evidence to support a recommendation