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Nursing & Allied Health

Research guide for Allied Health, ADN, BSN, and Human Services programs

What is a primary source?

A primary source is a document or record, usually a peer reviewed journal article, which reports a study, experiment, event or other phenomenon firsthand. Primary sources are usually written by the person(s) who did the research, conducted the study, ran the experiment, or witnessed the event.

Primary Sources include:

  • pilot/prospective studies
  • cohort studies
  • survey research
  • case studies, case series
  • qualitative studies
  • clinical trials and  randomized clinical trials/RCTs
NOTE: Read the Method section of an article to determine what kind of research was conducted. If you cannot find a section that details the method- you are probably not looking at a primary source.

Searching for Primary Sources (single studies) Unfiltered sources

Clinical Trials, Randomized Controlled Trials, Case Studies, cohort studies etc.

Check for filters to limit your search by study type. Look for clues in title or abstract. Read the "Method" section; if the author's methods only involve search for literature and analyzing publications that detail the clinical work of others, it is not a primary source.

What is a secondary source?

Secondary sources evaluate multiple primary studies so as to draw conclusions on or present our current state of knowledge in a discipline or subject. These are typically peer-reviewed before being published. Secondary sources typically include a bibliography which may direct you back to the primary research reported in the article.

Systematic Reviews and Meta-analyses are the most focused and the most comprehensive, which is why they are at the top of the evidence pyramid. 


 key characteristics of a systematic review are:

  • a clearly stated set of objectives with pre-defined eligibility criteria for studies;
  • an explicit, reproducible methodology;
  • a systematic search that attempts to identify all studies that would meet the eligibility criteria;
  • an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
  • a systematic presentation, and synthesis, of the characteristics and findings of the included studies.

Meta-analysis is the use of statistical methods to summarise the results of independent studies. By combining information from all relevant studies, meta-analyses can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review. Meta-analyses also facilitate investigations of the consistency of evidence across studies, and the exploration of differences across studies.

Cochrane Handbook 1.2.2

Searching for Secondary Sources, Filtered Sources

Systematic Reviews and Meta-analyses- the top of the EBP pyramid.

Use filters to limit your search by study type. Look for clues in the title or abstract. Read the "Method" section; if the authors conducted any clinical work it is not a systematic review or meta-analyisis.