The panel identified randomized controlled trials as the strongest level of evidence for the evaluation of treatment efficacy. However, in some instances, the panel had to make recommendations in the absence of RCTs. Category A therefore requires substantial numbers of studies involving substantial numbers of participants. Evidence is from endpoints of intervention studies that include only a limited number of RCTs, post hoc or subgroup analysis of RCTs, or meta-analysis of RCTs. In general, Category B pertains when few randomized trials exist, they are small in size, and the trial results are somewhat inconsistent, or the trials were undertaken in a population that differs from the target population of the recommendation.
Evidence is from outcomes of uncontrolled or nonrandomized trials or from observational studies.
Statements for which there is no available evidence are so indicated.