Physician Assistant Capstone Project: Relation to Evidence-Based Medicine

Putting Review Papers in the Context of EBM

In order to appreciate how medical review papers vary, it is important to recall the processing of evidence. Evidence is categorized based on how it has been processed and been packaged for use in clinical practice. They fall into the categories of Non-appraised Research, Critically Appraised Research, and Summaries/ Guidelines. The following content is based largely on  the 3rd edition of Users' guide to the medical literature: a manual for evidence-based clinical practice by Guyatt G, et. al, (2015).

• Non-appraised Research (also known as primary evidence or unfiltered evidence): these are individual studies or observations which may take the form of RCTs, other controlled or cohort trials, case reports, or case series. Some of the largest indexers of such studies and reports (aka databases) are PubMed (this includes MEDLINE), Embase, CINAHL, and Web of Science. Other databases include PsycINFO and the literature search element of ClinicalKey. Goolge Scholar may also be considered a source of on non-appraised research but it is not carefully built like the aforementioned databases and may bring in crowded results from non-biomedical disciplines.

• Critically Appraised Research (also known as secondary evidence or filtered evidence): these publications are the result of critical appraisal which is the process of "carefully and systematically assessing the outcome of scientific research (evidence) to judge its trustworthiness, value and relevance in a particular context" (CEBMa). To be even more precise, "critical appraisal looks at the way a study is conducted and examines factors such as internal validity, generalizability and relevance". Basically, pre-appraised research, is a look at the research that has been done and synthesized for you already. These take the form of syntheses and synopses.

• Syntheses often take two forms: (1) Systematic Reviews: seek to answer a defined clinical questions by using a predetermined search strategy with the goal of reducing bias by identifying, appraising, and synthesizing all relevant studies (of sound methodology) on a particular topic. (2) Meta-analyses: these are systematic reviews that "use statistical techniques to synthesize the data from several studies into a single quantitative estimate or summary effect size". These can be used when these is a enough data to statistically pool together and draw conclusions.

• Synopses: if you are lucky to find them (i.e., there are people and resources to write them), one-page synopses will quickly and concisely convey what some of the most significant systematic reviews and meta-analyses have concluded. Instead of reading the systematic review or meta-analysis yourself, you can turn to synopses for a meaningful explanation of what these authors of these large undertakings ultimately found. Some EBM pyramids will also include synopses of studies which may be helpful when no systematic reviews or meta-anlyses have been created yet, but you still want to find research that has been done on the topic.

• Summaries and Guidelines: these are regularly updated online resources (often found scattered across specialty journals and organization websites) that "integrate the body of evidence on a topic and aim to provide recommendations for optimal management" (Guyatt, 2015). Examples include clinical practice guidelines, clinical pathways, point-of-care tools, and evidence updates.

Review Papers are Syntheses

• A review paper is a type of synthesis.
• If you are being asked in class to write a literature review, you are in effect writing a synthesis.
• Refer to the 6S Pyramid of Evidence

Further Reading: User's Guide to the Medical Literature

Portions of this page have been mapped from our Evidence-Based Medicine Library Guide. Visit the guide for more details.