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. |