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 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 low level level of confidence:

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

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

• Strong

• Moderate

• Low

• Very Low

Strength of Recommendation

Determinants of Strength of Recommendation

• Quality of Evidence
• Balance between benefits, harms and burdens
• Patients values and preferences
• Resources and cost

Implication of Strength of Recommendation

Strong Recommendation

• Population : Most people in this situation would want the recommended course of action and only a small proportion would not.
• Healthcare workers: Most people should receive the recommended course of action.
• Policy makers: The recommendation can be adopted as a policy in most situations.

Weak Recommendation

• Population : Majority of the people in this situation would want the recommended course of action, but many would not .
• Healthcare workers: Be prepared to help people to make a decision that is consistent with their values/decision aids and shared decision making.
• Policy makers: There is a need for substantial debate and involvement of stakeholders.

IDSA 2016 Guidelines