"The most common definition of EBM is taken from Dr. David Sackett. EBM is "the conscientious, explicit and judicious use of current best evidence in making decisions about the care of the individual patient. It means integrating individual clinical expertise with the best available external clinical evidence from systematic research." (Sackett D, 1996)"

Read more at the UNC Introduction to Evidence-Based Medicine Tutorial

“As a distinctive approach to patient care, EBM involves two fundamental principles. First, evidence alone is never sufficient to make a clinical decision. Decision makers must always trade the benefits and risks, inconvenience, and costs associated with alternative management strategies, and in doing so consider the patient's values.  Second, EBM posits a hierarchy of evidence to guide clinical decision making.”

Read the complete text of JAMA's User's Guide to the Literature

The available evidence will change depending on the context of your search question.  If you need a quick answer for a patient then using one of the pre-filtered medical information resources such as BMJ Clinical Evidence or ACP PIER will be your best option.  If you are creating guidelines or need to examine the entire body of available evidence, then you will need to search multiple places to create a comprehensive search.  Searching the Research Medical Library’s selection of Top Picks will give you a very good picture of available evidence.  Most questions also have an associated subject-oriented database, such as CINAHL for nursing questions or Natural Standard for complementary, alternative or integrative medicine.  The list of EBM databases will give you additional options for searching.

When selecting evidence to consider, there are publication types which are more rigorous, transparent and replicatable.  The higher levels of evidence mitigate bias through their study design.  Mid-level evidence has more openings for bias due to study design, but this may be the highest available evidence for your particular question.  Low-level evidence is not sufficient for changing your practice; however, it may be all that is available for new research areas or understudied areas.  Finding only low-level evidence for your question may point to a potential research study for you to pursue.

Systematic review:a form of structure literature review that addresses a question that is formulated to be answered by analysis of evidence, and involves objective means of searching the literature, applying predetermined inclusion and exclusion criteria to this literature, critically appraising the relevant literature, and extraction and synthesis of data from evidence base to formulate findings.  

Meta-analysis:  systematic methods that use statistical techniques for combining results from different studies to obtain a quantitative estimate of the overall effect of a particular intervention or variable on a defined outcome. This combination may produce a stronger conclusion than can be provided by any individual study. (Also known as data synthesis or quantitative overview.)

Case-control study:  a retrospective observational study designed to determine the relationship between a particular outcome of interest (e.g., disease or condition) and a potential cause (e.g., an intervention, risk factor, or exposure). Investigators identify a group of patients with a specified outcome (cases) and a group of patients without the specified outcome (controls). Investigators then compare the histories of the cases and the controls to determine the rate or level at which each group experienced a potential cause. As such, this study design leads from outcome (disease or condition) to cause (intervention, risk factor, or exposure).

Cohort study: an observational study in which outcomes in a group of patients that received an intervention are compared with outcomes in a similar group i.e., the cohort, either contemporary or historical, of patients that did not receive the intervention. In an adjusted- (or matched-) cohort study, investigators identify (or make statistical adjustments to provide) a cohort group that has characteristics (e.g., age, gender, disease severity) that are as similar as possible to the group that experienced the intervention.