Systematic reviews, meta-analysis, and evidence-based medicine

Evidence-based medicine (EBM) is at the core of current clinical practice. The philosophical origins of EBM date as far back as the mid-19th century earlier. David Sackett (1934-2015) considered as the father of EBM, described it as 'the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients'. EBM requires that clinical decisions should be based on the evidence in totality, and not on just a single study. Systematic reviews offer the best available evidence for decision making in clinical practice. They are 'the most reliable and comprehensive statement about what works', and involve identifying, synthesising and assessing all available evidence by a systematic approach, to generate a robust, empirically derived answer to a focused research question. A systematic review may or may not contain a statistical analysis (Meta-analysis) depending on whether it is possible, and importantly, sensible to combine data from different studies on the same subject, or not. This chapter covers the history, principles and characteristics of systematic reviews and meta-analysis in the context of EBM.