IDSA guidelines classification scheme

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Strength of Recommendations

Class A

Good evidence to support a recommendation for or against use.

Class B

Moderate evidence to support a recommendation for or against use.

Class C

Poor evidence to support a recommendation.

Quality of Evidence

Level of Evidence I

Evidence from ≥1 properly randomized, controlled trial.

Level of Evidence 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.

Level of Evidence III

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

Applying Strength of Recommendations and Quality of Evidence

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Level of Evidence

Based on the different variables taken into account the level of evidence is rated by IDSA and it is as follows:

Factors favoring higher level of confidence:

• Randomized trails
• Large Effect
• Dose Response
• All plausible confounding and bias would reduce a demonstrated effect or would suggest a spurious effect if no effect was observed.

Factors favoring a low level level of confidence:

• Observational Studies
• Risk of Bias
• Inconsistency
• Indirectness
• Imprecision
• Publication Bias

Based on these considerations the level of evidence is rated as follows:

Strong

Moderate

Low

Very Low

Strength of Recommendation

Determinants of Strength of Recommendation