Evidence-based Medicine

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

Source: David Sackett, William Rosenberg, Muir Gray, Brian Haynes & Scott Richardson. Evidence based medicine: what it is and what it isn’t [internet]. BMJ; 13 January 1996 [cited 23 May 2013]. Available from: http://www.bmj.com/content/312/7023/71


Levels of evidence by study type

Level I - Evidence from a systematic review or meta-analysis of all relevant randomized controlled trials (RCTs)

Level II - Evidence obtained from well-designed RCTs

Level III - Evidence obtained from well-designed controlled trials without randomization

Level IV - Evidence from well-designed case-control and cohort studies

Level V - Evidence from systematic reviews of descriptive and qualitative studies

Level VI - Evidence from single descriptive or qualitative studies

Level VII - Evidence from the opinion of authorities and/or reports of expert committees

Source: Melnyk BM. Implementing the Evidence-Based Practice (EBP) Competencies in Healthcare : A Practical Guide to Improving Quality, Safety, and Outcomes. ; 2016. (Table 1.1, p. 11)


Article types explained

Empirical study (or primary article):  

  • Aims to gain new knowledge on a topic through direct or indirect observation and research. 
  • Include quantitative or qualitative data and analysis.
  • In science, an empirical article will often include the following sections: Introduction, Methods, Results, and Discussion.

Review article:  

  • Provides a synthesis of existing research on a particular topic. 
  • Useful when you want to get an idea of a body of research that you are not yet familiar with. 
  • Differs from a systematic review in that it does not aim to capture ALL of the research on a particular topic.

Systematic review:  

  • A methodical and thorough literature review focused on a particular research question. 
  • Aims to identify and synthesize all of the scholarly research on a particular topic in an unbiased, reproducible way to provide evidence for practice and policy-making. 
  • May involve a meta-analysis (see below). 


  • A type of research study that combines or contrasts data from different independent studies in a new analysis in order to strengthen the understanding of a particular topic. 
  • There are many methods, some complex, applied to performing this type of analysis.