Physician Assistant : Evidence Based Practice

Evidence based medicine (EBM) is the application of the best available research to clinical care, which requires the integration of evidence with clinical expertise and patient values.

Searching for evidence is an integral part of evidence based medicine. Searching effectively and efficiently is a skill which must be learned and cultivated like any other skill. This page includes tips and resources to help you in searching for evidence.

For database-specific tutorials, see Database Searching Tutorials. If you are conducting an evidence synthesis project, see our guide Systematic Reviews & Evidence Syntheses.

The Florida State University College of Medicine Charlotte Edwards Maguire Medical Library. Evidence Based Medicine Tutorial. "Definition of Evidence Based Medicine."  2011. Accessed 8-6-14.

Systematic Reviews
Address a focused clinical question where review authors systematically search for, identify, select, summarize and critically apraise all of the medical research literature available on a specific topic.  Statistical techniques may be used to combine the results of these studies.  The authors clearly state the search methods used to locate these studies.  It is important to examine the search methods used and decide for yourself if it was broad enough to include all of the relevant studies, and if the studies found were relevant to the clinical question.

Randomized Controlled Clinical Trial  (RCT)
An experimental design used for testing the effectiveness of a new medication or a new therapeutic procedure. Individuals are assigned randomly to a treatment group or a control group, and the outcomes are compared. RCT is the most accepted scientific method of determining the benefit of a drug or a therapeutic procedure. It represents the best evidence available, which is integrated into the final decision about the management of a condition by healthcare practitioners in what is called evidence-based healthcare.

Clinical Trial
The NIH defines a clinical trial as "a research study in which one or more human subjects are prospectively assigned to one or more interventions (which may include placebo or other control) to evaluate the effects of those interventions on health-related biomedical or behavioral outcomes."

Protocol
A protocol is a document which outlines the rationale, objectives, design, and methodology of a study.

Meta-Analysis
Meta-analysis is the statistical combination of results from two or more separate studies.

Review Article
Brings together information about previously published research on a topic.  It provides a critical appraisal of the topic over a period of time. It is helpful in identifying the important literature on a topic. Given the vast amount of scientific literature published, review articles are an excellent tool for researchers wishing to research a topic.

Searching is an iterative process; you're unlikely to create the perfect search on the first try. Follow the steps below to create a usable search string from a topic or research question.

Step 1: Extract the most relevant concepts from your topic or research question.

PICO is one framework used to help extract relevant concepts from a clinical research question.

P = Population / Problem / Patient

I = Intervention / Issue

C = Comparison / Control

O = Outcome

PICO is a tool to help you break down the question into concepts; whether or not you use PICO is not all that important. The important thing is to break down your research question into its component parts, one way or another.

Step 2: Term harvesting

Next, brainstorm alternative ways of phrasing each of your concepts. The goal here is for you to be able to use these alternative phrasings to create one high quality search which you can use to find the vast majority of relevant literature. Consider: synonyms, variant spellings, singular and plural forms, broader and more specific concepts, acronyms, and archaic terminology.

Step 3: Weave together your search string

With your lists of alternative phrasings in hand, you can now weave together your search string using boolean operators to connect your concepts. Your search string should look along the lines of:

(concept1 OR synonym) AND (concept2 OR synonym) AND (concept3 OR synonym)

Step 4: Search & iterate

As you search, you may notice additional phrasings for concepts which you hadn't originally considered. Add them into your search, within the appropriate concept group. If you are searching in PubMed, you may find it useful to include Mesh terms (PubMed's controlled vocabulary) in your search string. If you are finding too few results, you may want to remove one of your concept groups. If you are finding too many results, you may want to use the database's filters.

• ECRI Guidelines Trust

Grey literature can be described as any information produced outside of traditional publishing channels--essentially anything besides articles published in scholarly journals. Grey literature can include, but is not limited to: pre-prints, reports, white papers, theses, conference proceedings, technical specifications and standards, technical and commercial documentation, and government documents. For this reason, frey literature can be difficult to systematically search for and evaluate.

Learn more below:

"Grey literature." (Institute for Work and Health).

"Grey literature: What it is & how to find it." (Simon Fraser University).