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Table 1 Levels of evidence and recommendation

From: Evidence levels in radiology: the insights into imaging approach

Levels of evidence and recommendation

Level of evidence

Confidence in the evidence and recommendations grade

High

Data derived from metanalyses or systematic reviews or from (multiple) randomized trials with high quality

Large retrospective observational studies or in silico clinical trials with external validation

Well defined reference standards and controlled biases

The described technique improves healthcare pathway (tests, treatment, hospitalization) or decreases costs per patient

Level is graded down to Moderate if there are limiting biases or inconsistencies between studies

Further research is unlikely to change our confidence in the estimate of benefit and risk

Strongly recommended, mainly if presumed important patient outcomes and/or acceptable costs

Wording associated with the High grade of recommendation: ‘‘must”, ‘‘should” “recommend”

Moderate

Data derived from a single large randomized clinical trial or multiple nonrandomized studies

Large retrospective observational multicentre studies or large in silico clinical trials with controlled design and internal validation. Appropriate spectrum of cases

Studies on technique assessments of noninferiority, surrogate biomarkers or changes in clinical management

Level can be upgraded to High if there is a demonstrated large effect size or downgraded if the effect size is small

Further research is likely to have an impact on our confidence in the estimate of benefit and risk and may change the estimate

Recommendation is modulated to strong or weak by the presumed patient outcomes and final costs

Low

Small series, non-validated results and single centre observational, experimental or technical studies

None or imperfect reference standards

No study on the validation of results

Large possible biases

Opinions, general statements, critical and educational reviews without analytical methods

Studies on either technical efficacy or diagnostic validation accuracy (reference standards)

Any estimate of effect is uncertain

Weak recommendation, mainly if not clear patient important outcomes and/or high cost

Wording associated with the Low grade of recommendation: ‘‘could”, ‘‘may”, “suggests”