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Table 1 Classification of evidence and recommendation

From: Chemoprophylaxis, diagnosis, treatments, and discharge management of COVID-19: An evidence-based clinical practice guideline (updated version)

Grade of Recommendation Strength of the recommendation: Benefits vs. risks, harms, and burdens (Grade 1 or 2) State of the scientific evidence: Methodologic strength of supporting evidence (Grade A, B, or C)a Implications
1A:Strong recommendation, high-quality evidence Benefits clearly outweigh risk and burden, or vice versa Consistent evidence from RCTs without important limitations or exceptionally strong evidence from observational studies Recommendation can apply to most patients in most circumstances. Further research is very unlikely to change our confidence in the estimate of effect
1B: Strong recommendation, moderate-quality evidence Benefits clearly outweigh risk and burden, or vice versa Evidence from RCTs with important limitations (inconsistent results, methodologic flaws, indirect or imprecise), or very strong evidence from observational studies Recommendation can apply to most patients in most circumstances. Higher quality research may well have an important impact on our confidence in the estimate of effect and may change the estimate
1C: Strong recommendation, low or very low-quality evidence Benefits clearly outweigh risk and burden, or vice versa Evidence for at least one critical outcome from observational studies, case series, or from RCTs with serious flaws or indirect evidence Recommendation can apply to most patients in many circumstances. Higher quality research is likely to have an important impact on our confidence in the estimate of effect and may well change the estimate
2A: Weak recommendation, high-quality evidence Benefits closely balanced with risks and burden Consistent evidence from
RCTs without important limitations or exceptionally strong evidence from observational studies
The best action may differ depending on circumstances or patients’ or societal values. Further research is very unlikely to change our confidence in the estimate of effect
2B: Weak recommendation, moderate-quality evidence Benefits closely balanced with risks and burden Evidence from RCTs with important limitations (inconsistent results, methodologic flaws, indirect or imprecise), or very strong evidence from observational studies Best action may differ depending on circumstances or patients’ or societal values. Higher quality research may well have an important impact on our confidence in the estimate of effect and may change the estimate.
2C: Weak recommendation, low or very low-quality evidence Uncertainty in the estimates of benefits, risks, and burden; benefits, risk, and burden may be closely balanced Evidence for at least one critical outcome from observational studies, case series, or from RCTs with serious flaws or indirect evidence Other alternatives may be equally reasonable. Higher quality research is likely to have an important impact on our confidence in the estimate of effect and may well change the estimate
Ungraded consensus-based statement Uncertainty due to lack of evidence but expert opinion that benefits outweigh risk and burdens or vice versa Insufficient evidence for a graded recommendation Future research may well have an important impact on our confidence in the estimate of effect and may change the estimate
  1. aGuideline panels determine the overall quality of evidence across all the critical outcomes essential based on: 1) If the quality of evidence is the same for all critical outcomes, then this becomes the overall quality of the evidence supporting the answer to the question; 2) If the quality of evidence differs and there is inconsistent results across critical outcomes, the interval quality of evidence is supplied; 3) If the quality of evidence differs and there is consistent results across critical outcomes, the lowest quality of evidence for any of the critical outcomes determines the overall quality of evidence