Empirical methods for systematic reviews and evidence-based medicine

Evidence-Based Medicine is the integration of best research evidence with clinical expertise and patient values. Systematic reviews have become the cornerstone of evidence-based medicine, which is reflected in the position systematic reviews have in the pyramid of evidence-based medicine. Systematic reviews are exhaustive summaries of all studies relevant to answer a specific research question. The advantage of systematic reviews over single primary studies is that they give a structured and transparent overview of all available evidence and its quality, following strict methods. If possible, a meta-analysis can be performed in which the results of all relevant studies are combined to provide an overall estimate of the effect. The strength of the conclusions is based on the overall rating of confidence in the estimated effects, which is only relevant in settings when recommendations for clinical practice are made. This overall confidence depends on methodological limitations of the primary studies, inconsistency of the results (heterogeneity), indirectness of the evidence (applicability), imprecision of the effect estimates and possible reporting biases. This thesis was undertaken to contribute to the development of methods of systematic reviews