• Evidence-Based Practice
• Health
• Methods
• Systematic Reviews as Topic

The aphorism suggesting that we should keep things as simple as possible but not simpler applies well to the world of evidence-based medicine (EBM). The initial Users’ Guide to the Medical Literature that launched the era of EBM adhered faithfully to the as-simple-as-possible rule. For instance, the first Users’ Guide to therapy published in JAMA in 1993 presenting appraisal guidance for studies of interventions offered only two primary and two secondary validity (now risk of bias) criteria and was little more than three pages in length.1 The guides that followed adhered to the same parsimonious presentations, short and with few criteria. That simplicity in part explains EBM’s extraordinarily rapid and extensive uptake, with the Users’ Guides series and subsequently the associated textbook2 widely adopted in undergraduate and postgraduate medical programmes in a matter of just a few years.

Following the initial focus on critical appraisal for clinicians, EBM leaders became aware that few would ever be in a position to evaluate primary studies (insufficient training, insufficient time).3 Clinicians therefore turned to systematic reviews and clinical practice guidelines. Landmarks of this next phase of EBM included the establishment of the Cochrane Collaboration and elaboration of the principles of trustworthy guidelines. The methodology underlying EBM now included instruments addressing risk of bias in randomised trials and observational studies, and grading quality of evidence and strength of recommendations (GRADE) methodology for assessing certainty of evidence and moving from evidence to recommendations. In the last decade, however, leaders in the field have lost sight of the balance between simplicity and methodological sophistication in these methods.