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Public Health

Evidence Based Practice

Evidence-Based Practice or Evidence-Based Medicine is the integration of best research evidence with clinical expertise and patient values. (Sackett DL, Straus SE, Richardson WS, et al. Evidence-based medicine: how to practice and teach EBM. 2nd ed. Edinburgh: Churchill Livingstone, 2000.)

Research articles found in library resources contain evidence you will use for clinical decision-making. You will find and use many types of sources as you search for evidence. 

Pyramid diagram for types of research articles arranged with increasing quality of evidence.

EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved.
Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.

Types of Sources

Primary Research

Randomized Controlled Trials are studies in which subjects are randomly assigned to two or more groups; one group receives a particular treatment while the other receives an alternative treatment (or placebo). Patients and investigators are "blinded", that is, they do not know which patient has received which treatment. This is done in order to reduce bias.

Cohort Studies are cause-and-effect observational studies in which two or more populations are compared, often over time. These studies are not randomized.  

Case Control Studies study a population of patients with a particular condition and compare it with a population that does not have the condition. It looks the exposures that those with the condition might have had that those in the other group did not.

Cross-Sectional Studies look at diseases and other factors at a particular point in time, instead of longitudinally. These are studies are descriptive only, not relational or causal. A particular type of cross-sectional study, called a Prospective, Blind Comparison to a Gold Standard, is a controlled trial that allows a research to compare a new test to the "gold standard" test to determine whether or not the new test will be useful.

Case Studies are usually single-patient cases.  

Secondary Research

Systematic Reviews are studies in which the authors ask a specific clinical question, perform a comprehensive literature search, eliminate poorly done studies, and attempt to make practice recommendations based on the well-done studies. (Note: systematic reviews are still considered original research because they contain a study design.)

Meta-Analyses are systematic reviews that combine the results of select studies into a single statistical analysis of the results.

Clinical Practice Guidelines are systematically developed statements used to assist practitioners and patients in making healthcare decisions.  

(Adapted from Salem State University Evidence-Based Medicine (EBM) Research Guide)

Search with MeSH Headings

MeSH (Medical Subject Headings), the National Library of Medicine's controlled vocabulary thesaurus, consists of terms naming descriptors in a hierarchical structure that permits searching at various levels of specificity.

In other words, MeSH terms describe what an article is about and are used to label all articles on a topic even if different authors use different words for the same concept (such as cancer vs. neoplasm vs. tumor).

Use MeSH to Search

PICO Research Questions

Use the PICO acronym to help you form a research question. These categories will help you consider all the angles of your topic and come up with keywords to use when searching in a database. 

P: Patient, Population, or Problem

I: Intervention (or Exposure) 

C: Comparison (or Control)

O: Outcome 

Note that you might not have a C, or your C might be the absence of your Intervention. Considering the Comparison will still help you search for your topic.