Table 1.

  Infectious Diseases Society of America–U.S. Public Health Service Grading System for Ranking Recommendations in Clinical Guidelines

Category, Grade	Definition
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
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 analytical 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 of expert committees

NOTE. Adapted from Canadian Task Force on the Periodic Health Examination. ²