TABLE 2

Infectious Diseases Society of America/US Public Health Service Grading System for Ranking Recommendations for Clinical Guidelines

Category, GradeDefinition
Strength of recommendation
 A Good evidence to support a recommendation for use
 B Moderate evidence to support a recommendation for use
 C Poor evidence to support a recommendation for use
Quality of evidence
 I Evidence from ≥1 properly randomized controlled trial
 II Evidence from ≥1 well-designed clinical trial, without randomization; from cohort or case-controlled analytic studies (preferably from >1 center); from multiple time series; or from dramatic results from uncontrolled experiments
 III Evidence from opinions of respected authorities, based on clinical experience, descriptive studies, or reports from expert committees