Table 1.

Approach of guidelines to grading recommendations

Guideline	Approach
American Society of Clinical Oncology
Type of recommendation	Evidence based: Sufficient evidence to inform clinical practice (based upon assessment of aggregate risk of bias, consistency of results, directness of evidence, and precision of results). Formal consensus: Insufficient evidence to inform a recommendation. Panel used a formal consensus process to reach the recommendation that represents best current guidance for practice. Informal consensus: Insufficient evidence to inform a recommendation. The recommendation represents best practice based upon an informal consensus of the panel. No recommendation: Insufficient evidence, confidence, or agreement to provide a recommendation to guide clinical practice.
Rating the strength of recommendation	Strong: High degree of confidence that the recommendation reflects best practice based upon (a) strong evidence for true net effect, (b) consistent results, (c) minor or no concerns about study quality, (d) the extent of panelists’ agreement. Moderate: Moderate confidence that the recommendation represents best practice based upon (a) good evidence for true net effect, (b) consistent results, (c) minor or few concerns about study quality, (d) extent of panelists’ agreement. Weak: Some confidence that the recommendation offers best current guidance for practice based upon (a) limited evidence, (b) consistent results but important exceptions, (c) concerns about study quality, (d) panelists’ agreement.
International Initiative on Thrombosis and Cancer
Levels of evidence	High: Further research very unlikely to change our confidence in the estimate of effect. Moderate: Further research is further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low: Any estimate of effect is very uncertain.
Levels of recommendation	Strong: The panel is confident that the desirable effects of adherence to a recommendation outweigh the undesirable effects. Weak: The panel concludes that the desirable effects of adherence to a recommendation probably outweigh the undesirable effects but is not confident. Best clinical practice (guidance): In the absence of any clear scientific evidence and because of the undetermined balance between desirable and undesirable effects, judgment was based on the professional experience and consensus of the international experts within the working group.
National Comprehensive Cancer Network: Strength of recommendations	Category 1: Based upon high‐level evidence (multiple adequately powered randomized controlled trials with consistent results) and uniform consensus (≥85% agreement) of the guideline committee that the intervention is appropriate. Category 2A: Based upon lower‐level evidence and uniform National Comprehensive Cancer Network consensus (≥85% agreement) that the intervention is appropriate. Category 2B: Based upon lower‐level evidence and less than uniform consensus (>50% but <85% of the panel vote) that the intervention is appropriate. Category 3: Based upon any level of evidence with major disagreement (<50% of panel) that the intervention is appropriate.
Spanish Society of Medical Oncology
Strength of recommendation	A: Good evidence to support a recommendation for use. B: Moderate evidence to support a recommendation for use. C: Poor evidence to support a recommendation for use. D: Moderate evidence to support a recommendation against use. E: Good evidence to support a recommendation against use.
Quality of evidence	I: Evidence from at least one properly randomized controlled trial. II: Evidence from at least one well‐designed clinical trial, without randomization; from cohort or case‐controlled analytic studies (preferably from more than one center); from multiple time series; or from dramatic results from uncontrolled experiments. III: Evidence from opinions of respected authorities, based on clinical experience, descriptive studies, or reports of expert committees.