Evidence category | Sources of evidence | Definition |
---|---|---|
A | Meta-analyses, position-stands, and randomized-controlled trials (RCTs) | Evidence from meta-analyses, position stands, and well-designed RCTs (or trials that depart only minimally from randomization) that provide a consistent pattern of findings in the population for which the recommendation is made. |
B | Systematic reviews including RCTs of limited number | Evidence from endpoints of intervention studies that include only a limited number of RCTs, post hoc or subgroup analysis of RCTs. In general, Category B is relevant when few randomized trials exist, they are small in size, and/or the trial results are somewhat inconsistent. |
C | Nonrandomized trials/observational studies, other reviews (e.g., narrative) | Evidence from outcomes of uncontrolled/nonrandomized trials or from observational studies. Reviews that may harbour a specific narrative. |
D | Case-reports | Evidence from low number or single-subject designs that report on unique observations or events, not necessarily applicable to broader populations. |