Table 1—

Description of levels of evidence

Evidence categorySources of evidenceDefinition
ARCTsRich body of dataEvidence is from end-points of well-designed RCTs that provide a consistent pattern of findings in the population for which the recommendation is madeCategory A requires substantial numbers of studies involving substantial numbers of participants
BRCTsLimited body of dataEvidence is from end-points of intervention studies that include only a limited number of patients, post hoc or subgroup analysis of RCTs, or meta-analysis of RCTsIn general, category B is assigned when few randomised trials exist, they are small in size, they were undertaken in a population that differs from the target population of the recommendation, or the results are somewhat inconsistent
CNonrandomised trialsObservational studiesEvidence is from outcomes of uncontrolled or nonrandomised trials or from observational studies
DPanel consensus judgementThis category is used only in cases where the provision of some guidance was deemed valuable but the clinical literature addressing the subject was deemed insufficient to justify placement in one of the other categoriesThe panel consensus is based on clinical experience or knowledge that does not meet the aforementioned criteria
  • RCT: randomised controlled trial.