| Table 4. Size of treatment effect
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Class I
Benefit >>> Risk
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Class IIa
Benefit >> Risk
Additional studies with focused objectives needed
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Class IIb
Benefit ≥ Risk
Additional studies with broad objectives needed; additional registry data would be helpful
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Class III
Benefit ≥ Risk
No additional studies needed
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Procedure/treatment should be performed/administered
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It is reasonable to perform/administer treatment
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Procedure/treatment may be considered
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Procedure/treatment should not be performed/administered since it is not helpful and may be harmful
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| Level A
Multiple (3-5) population risk strata evaluated
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- Recommendation that procedure or treatment is useful/effective
- Sufficient evidence from multiple randomized trials or non-randomized trials
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- Recommendation in favor of treatment or procedure being useful/effective
- Some conflicting evidence from multiple randomized trials or meta-analyses
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- Recommendation’s usefulness/efficacy less well established
- Greater conflicting evidence from multiple randomized trials or meta-analyses
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- Recommendation that procedure or treatment not useful/effective and may be harmful
- Sufficient evidence from multiple randomized trials or meta-analyses
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| Level B
Limited (2-3) population risk strata evaluated
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- Recommendation that procedure or treatment is useful/effective
- Limited evidence from single randomized trial or non-randomized studies
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- Recommendation in favor of treatment or procedure being useful/effective
- Some conflicting evidence from single randomized trial or non-randomized studies
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- Recommendation’s usefulness/efficacy less well established
- Greater conflicting evidence from single randomized trial or non-randomized studies
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- Recommendation that procedure or treatment not useful/effective and may be harmful
- Limited evidence from single randomized trial or non-randomized studies
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| Level C
Very limited (1-2) population risk strata evaluated
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- Recommendation that procedure or treatment is useful/effective
- Only experts opinion, case studies, or standard-of-care
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- Recommendation in favor of treatment or procedure being useful/effective
- Only diverging expert opinion case studies, or standard-of-care
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- Recommendation’s usefulness/efficacy less well established
- Only diverging expert opinion case studies, or standard-of-care
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- Recommendation that procedure or treatment not useful/effective and may be harmful
- Only expert opinion case studies, or standard-of-care
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