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Read more on scientific trials
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Last modified date: Saturday, 12 April 2008
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Natural Standard evidence-based validated grading rationale™
| • | Grades reflect the level of available scientific evidence in support of the efficacy of a given therapy for a specific indication. | | • | Expert opinion and folkloric precedent are not included in this assessment, and are reflected in a separate section of each monograph ("Strength of Expert Opinion and Historic/Folkloric Precedent"). | | • | Evidence of harm is considered separately; the below grades apply only to evidence of benefit. |
| | Level of Evidence Grade | Criteria | | A (Strong Scientific Evidence) | | Statistically significant evidence of benefit from >2 properly randomized trials (RCTs), OR evidence from one properly conducted RCT AND one properly conducted meta-analysis, OR evidence from multiple RCTs with a clear majority of the properly conducted trials showing statistically significant evidence of benefit AND with supporting evidence in basic science, animal studies, or theory. | | B (Good Scientific Evidence) | Statistically significant evidence of benefit from 1-2 properly randomized trials, OR evidence of benefit from >1 properly conducted meta-analysis OR evidence of benefit from >1 cohort/case-control/non-randomized trials AND with supporting evidence in basic science, animal studies, or theory. | | C (Unclear or conflicting scientific evidence) | Evidence of benefit from >1 small RCT(s) without adequate size, power, statistical significance, or quality of design by objective criteria,* OR conflicting evidence from multiple RCTs without a clear majority of the properly conducted trials showing evidence of benefit or ineffectiveness, OR evidence of benefit from >1 cohort/case-control/non-randomized trials AND without supporting evidence in basic science, animal studies, or theory, OR evidence of efficacy only from basic science, animal studies, or theory. | | D (Fair Negative Scientific Evidence) | Statistically significant negative evidence (i.e., lack of evidence of benefit) from cohort/case-control/non-randomized trials, AND evidence in basic science, animal studies, or theory suggesting a lack of benefit. | | F (Strong Negative Scientific Evidence) | Statistically significant negative evidence (i.e. lack of evidence of benefit) from >1 properly randomized adequately powered trial(s) of high-quality design by objective criteria.* | | Lack of Evidence† | Unable to evaluate efficacy due to lack of adequate available human data. |
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