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]. 

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.

Study design resources and reporting requirements 

The PICO Framework

The PICO Framework can be used to structure and refine your research question. This can then be used to structure your search strategy and your process for identifying articles of interest.