Skip to Main Content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.

Physician Assistant: Evidence Based Practice

A guide to physician assistant library resources and research

PICO Worksheet

EBP Resources

Clinical Trial Registries

What is Evidence Based Medicine?

EBM Triad
Triad From: 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.


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.


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
an experiment performed on human beings in order to evaluate the comparative efficacy of two or more therapies. 

In the Cochrane Library database, the protocol outlines the question that the review authors are addressing, detailing the criteria against which studies will be assessed for inclusion in the review, and describing how the authors will manage the review process.

When results of individual studies are combined to produce an overall statistic.

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.

Practice Guidelines

Grey Literature

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).

Filtered Resources

Filtered Resources appraise the quality of studies and often make recommendations for practice. 

Systematic Reviews and Meta-Analyses
Authors of systematic reviews ask a specific clinical question, perform a comprehensive search of the literature, eliminate poorly done studies and make practiced recommendations based on the well-done studies.

A meta-analysis is a systematic review that combines the results of all the studies into one statistical analysis of results.

Critically Appraised Topics
Authors evaluate and synthesize multiple research studies.

Critically Appraised Individual Articles
Authors evaluate individual research studies.

Looking to Find Systematic Reviews?

There are a number of places to look for systematic reviews, including within the commonly used databases listed on this page. Some other resources to consider are: