Box 2.

: Quality of evidence rating system (adapted from National Health and Medical Research Council¹⁵)

• Level 1—Evidence obtained from a review of all relevant randomised controlled trials
• Level 2—Evidence obtained from at least one randomised controlled trial
• Level 3—Evidence obtained from controlled trials without randomisation
• Level 4—Evidence obtained from multiple time series with or without intervention
• Level 5—Other evidence (such as opinions or policies of respected authorities based on clinical experience, descriptive studies, or reports of expert committees; summary by writers using a variety of written material; expert testimony; reference to the philosophy of a particular practitioner; reference to personal experience)