Rules of Evidence
and
Categories of Recommendations

Rules of Evidence

I: Evidence obtained from at lease one properly randomized controlled trial

II-1: Evidence obtained from properly controlled non-randomized trials

II-2: Evidence from well-designed cohort or case control analytic studies, preferably from more than one center or research group

II-3: Evidence obtained from multiple time series studies with or without the intervention. Dramatic results in uncontrolled experiments (such as the results of the introduction of penicillin in the 1940s) could also be regarded as this type of evidence

III: Opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees

 

Categories of Recommendations

A: There is good evidence to support the recommendation

B: There is fair evidence to support the recommendation

C: There is poor evidence regarding the inclusion or exclusion of the recommendation, and may be made on other grounds

D. There is fair evidence to support excluding the recommendation

E. There is good evidence to support excluding the recommendation

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