Systematic Reviews: How they are different from narrative reviews and how you can do one.

Systematic Reviews v. Narrative Reviews, what's the difference?Before 2005, the secondary literature was a monodominant landscape in veterinary medicine composed of the narrative review.The narrative review is the summary of knowledge and literature from an expert in the field.A clever analogy is to think ofnarrative reviews as "free-floating book chapters" (Personal Communication, Luis Arroyo).After the adoption of Evidence-based Medicine (EBM) and subsequently Evidence-based Veterinary Medicine (EBVM or EVM), the narrative reviews were perceived by many to be removed from the hierarchy of secondary literature as being biased and without the rigor and information that can be offered by a systematic review 1 .Secondary evidence synthesis has become a very broad landscape with more and more types of reviews being described which can range in number from 14 -38 3,4 .It may be important to appreciate that many of these review types overlap and can be complementary of each other.For instance, a scoping review or narrative review are not trying to do accomplish the same things as a systematic review.Understanding the type of research question will reflect on which review is most useful.For an overview or answering background questions on a topic, a narrative review should probably be the first stop.To address foreground or specific clinical questions, systematic reviews are best 5 .Of the fourteen review types mentioned, this author feels these are the most common in veterinary medicine (see Chart One):Narrative Review:: These are usually considered to be literature reviews or state of the art reviews, but are unified by usually being written by an expert in the field with salient selection of articles that are influencing the field today.These have been increasingly expected to be performed by journal invitation (or solicitation).Usually no methods are available because this is an expert sharing the state of the field in their opinion 1,3,4 .Critically Appraised Topic (Rapid Review, Knowledge Summary, Best Bet) -these can be written by an expert or group of experts, many elements of a systematic review are here: an answerable question in PICO format (Patient, Intervention, Comparison, Outcome), reported search strategy (although more specific in design to yield only relevant articles), inclusion and exclusion criteria, Some degree of critical appraisal of articles ability to answer the research question and a final bottom line of clinical applicability based on this evidence 3,6,7 .Integrative Review (systematized review) -Much deeper research with a systematized search that should be sensitive and broad (like include other languages and grey literature like PhD theses or conference proceedings).Clear inclusion/exclusion criteria and often some critical appraisal tool to summarize content.This is an approach often undertaken by graduate students 3,4,[8][9][10][11][12][13][14] .Scoping Review -should have 3 authors, two screeners and an arbiter.A published Protocol on SYREAF or OSF, a sensitive search strategy across at least 3 databases , inclusion or exclusion criteria +/-risk of bias assessment of included studies.Data is characterized versus extracted since this is describing the body of research, not necessarily making statements about the results 3,15 .Systematic Review -considered the gold standard of evidence synthesis where it answers a specific clinical question (PICO).Should have a published protocol on SYREAF or OSF, Three authors (Two screeners and arbiter), sensitive and complete search -minimum three databases, a risk of bias tool to evaluate study quality, may include statistical summary or meta-analysis 3,15 .Umbrella Review -This is a systematic review of systematic review studies.While present in human medical literature, virtually non-existent in veterinary 3 .