<P> Systematic reviews are a type of literature review that uses systematic methods to collect secondary data, critically appraise research studies, and synthesize studies . Systematic reviews formulate research questions that are broad or narrow in scope, and identify and synthesize studies that directly relate to the systematic review question . They are designed to provide a complete, exhaustive summary of current evidence relevant to a research question . Systematic reviews of randomized controlled trials are key to the practice of evidence - based medicine, and a review of existing studies is often quicker and cheaper than embarking on a new study . </P> <P> An understanding of systematic reviews, and how to implement them in practice, is highly recommended for professionals involved in the delivery of health care . Besides health interventions, systematic reviews may examine clinical tests, public health interventions, environmental interventions, social interventions, adverse effects, and economic evaluations . Systematic reviews are not limited to medicine and are quite common in all other sciences where data are collected, published in the literature, and an assessment of methodological quality for a precisely defined subject would be helpful . </P> <P> A systematic review aims to provide a complete, exhaustive summary of current literature relevant to a research question . The first step in conducting a systematic review is to create a structured question to guide the review . The second step is to perform a thorough search of the literature for relevant papers . The Methodology section of a systematic review will list all of the databases and citation indexes that were searched such as Web of Science, Embase, and PubMed and any individual journals that were searched . The titles and abstracts of identified articles are checked against pre-determined criteria for eligibility and relevance to form an inclusion set . This set will relate back to the research problem . Each included study may be assigned an objective assessment of methodological quality preferably by using methods conforming to the Preferred Reporting Items for Systematic Reviews and Meta - Analyses (PRISMA) statement (the current guideline) or the high quality standards of Cochrane . </P> <P> Systematic reviews often, but not always, use statistical techniques (meta - analysis) to combine results of eligible studies, or at least use scoring of the levels of evidence depending on the methodology used . An additional rater may be consulted to resolve any scoring differences between raters . Systematic review is often applied in the biomedical or healthcare context, but it can be applied in any field of research . Groups like the Campbell Collaboration are promoting the use of systematic reviews in policy - making beyond just healthcare . </P>

Quantitative systematic reviews include what type of study designs