Once rather a niche business, evidence-based medicine (EBM) as an approach to clinical decision-making requiring the integration of the best available research evidence with individual clinical expertise and patient values, has gained widespread acceptance and support within the healthcare community. This review article covers the basic principles of systematic reviews and meta-analyses, and their role in the process of evidence-based decision-making. The strengths and weaknesses of traditional narrative reviews are discussed, as well as the way systematic reviews limit bias associated with the assembly, critical appraisal and synthesis of studies addressing specific clinical questions. The authors provide a step-by-step introduction for the most relevant issues in writing a systematic review from the initial formulation of a research question according to the PICO-rule to sensitivity analyses in conjunction with the combined analysis of the pooled data. Special emphasis is put on important issues that need to be considered when appraising a systematic review or meta-analysis, thus providing a description on how to use systematic reviews for clinical decision-making. Some of the terms that are frequently used in the reporting of systematic reviews and meta-analyses, such as relative risk, confidence interval, Forest plot or L'Abbé plot, will be introduced and explained.
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