Table 2

Classification of treatment benefit level

QuestionLevel 1Level 2Level 3Level 4Level 5
Does this intervention help? (treatment benefits)Systematic review of randomised controlled trial or n-of-1 trialRandomised controlled trial or observational study with dramatic effectNon-randomised controlled cohort/follow-up studyCase-series, case-control, or historically controlled studiesMechanism-based reasoning
  • Adapted from: Oxford Centre for Evidence Based Medicine (OCEBM)—Levels of Evidence Working Group. ‘The Oxford 2011 Levels of Evidence’. Oxford Centre for Evidence-Based Medicine. http://www.cebm.net/index.aspx?o=5653.