Skip to Main Content

Evidence-Based Medicine

An Introduction to EBM

A definition

"Evidence-based medicine is the conscientious explicit and judicious use of current best evidence in making decisions about the care of individual patients."

Sackett DL. Evidence-based medicine. Seminars in Perinatology. 1997 Feb;21(1):3-5. doi: 10.1016/s0146-0005(97)80013-4.

Study Designs

Background Information and Expert Opinion:

Background information is important to consult when you need general information about a condition, medication, or diagnostic test.

Case Reports or Case Series

Case Series reports usually include only a few participants who are given a similar intervention and follow-up.   Case Control Studies look retrospectively at individuals and compare with a similar group who did not have the intervention.  These studies are conducted in the early stages of research to help identify variables that might predict a condition.  One of the weaknesses in these designs is that there are small numbers of participants and they are frequently not randomized or controlled for confounding variables.

Cohort Studies

Also called longitudinal or epidemiological studies, Cohort studies follow a large group of people over an extended period of time to see how their exposures affect their outcomes. This type of study is normally used to look at the effect of suspected risk factors that cannot be controlled experimentally – for example, the effect of smoking on lung cancer.

Cohort studies may include a second group that did not engage in the same intervention as a control comparison.  These studies can be difficult to blind, can’t be controlled for outside variables, and are usually not randomized.

Randomized Control Trial (RCT)

Randomized Control Trials are based on experimental design where individuals are assigned by special randomization techniques into two or more groups, where one group receives the intervention under investigation and the other(s) receives no treatment, a placebo, or a standard intervention.

A large Double Blinded Randomized Control Trial is the most reliable “test” or study design and provides the strongest support of a cause and effect relationship.

Critically Appraised Topics (CATS)

Critically appraised topics are not studies but are short summaries of the best available evidence.

Systematic Reviews and Meta-Analysis

Systematic reviews analyze and appraise the evidence about an intervention, comparing the results of studies side by side, typically on a forest plot. Systematic reviews are considered the strongest and highest quality of evidence.

A meta-analysis reviews multiple studies and a statistical summary is made that represents the effect of the intervention across multiple studies.



Evidence Pyramid: Hierarchy of Evidence

Foreground Questions/Filtered Information:  Cochrane Library, DynaMed, Essential Evidence Plus, Up to Date

Background Questions/Unfiltered Information: AccessMedicine, CINAHL, ClinicalKey, PubMed, Rutgers Libraries e-books collections


© , Rutgers, The State University of New Jersey

Rutgers is an equal access/equal opportunity institution. Individuals with disabilities are encouraged to direct suggestions, comments, or complaints concerning any accessibility issues with Rutgers websites to or complete the Report Accessibility Barrier / Provide Feedback form.