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TABLE 1

Classification of Recommendations and Level of Evidence

Classification of recommendations 
    Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is beneficial, useful, and effective and should be performed. Benefit>>>risk. 
    Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment. 
        Class IIa: Weight of evidence/opinion is in favor of usefulness/efficacy. It is reasonable to perform procedure/administer treatment. Benefit>>risk. Additional studies with focused objectives needed. 
        Class IIb: Usefulness/efficacy is less well established by evidence/opinion. Procedure/treatment may be considered. Benefit≥risk. Additional studies with broad objectives needed; additional registry data would be helpful. 
    Class III: Conditions for which there is evidence and/or general agreement that a procedure/treatment is not useful/effective and in some cases may be harmful. Risk≥benefit. No additional studies needed. Procedure/treatment should not be performed/administered because it is not helpful and may be harmful. 
Level of evidence 
    A: Data derived from multiple randomized clinical trials or meta-analyses 
    B: Data derived from a single randomized trial or nonrandomized studies 
    C: Only consensus opinion of experts, case studies, or standard of care 
Classification of recommendations 
    Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is beneficial, useful, and effective and should be performed. Benefit>>>risk. 
    Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment. 
        Class IIa: Weight of evidence/opinion is in favor of usefulness/efficacy. It is reasonable to perform procedure/administer treatment. Benefit>>risk. Additional studies with focused objectives needed. 
        Class IIb: Usefulness/efficacy is less well established by evidence/opinion. Procedure/treatment may be considered. Benefit≥risk. Additional studies with broad objectives needed; additional registry data would be helpful. 
    Class III: Conditions for which there is evidence and/or general agreement that a procedure/treatment is not useful/effective and in some cases may be harmful. Risk≥benefit. No additional studies needed. Procedure/treatment should not be performed/administered because it is not helpful and may be harmful. 
Level of evidence 
    A: Data derived from multiple randomized clinical trials or meta-analyses 
    B: Data derived from a single randomized trial or nonrandomized studies 
    C: Only consensus opinion of experts, case studies, or standard of care 
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