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Drexel Library

Primary vs Secondary Literature in the Biomedical Sciences

Types of Sources

When searching the biomedical literature, you will find two main categories of articles: Primary and Secondary. Primary sources include articles that describe original research. Secondary sources interpret or analyze those primary sources.

Primary Source Characteristics

Primary sources that describe original research, clinical trials for example, will be published as peer-reviewed journal articles. But this does not mean that all journal articles are primary sources. Primary articles will describe one research project or study. The text of the article will include, at minimum:

  • an introduction with a statement of the research objective,
  • a methods section that details exactly how the research was performed, with enough information that another researcher could replicate it
  • a results section that describes the data collected, including charts or graphs and statistical analysis
  • a discussion section that interprets the results within the context of the research objective.

These elements are usually summarized in a structured abstract, in which the abstract is split into sections, although not all journals required structured abstracts.

Secondary Source Characteristics

Secondary sources are best identified by their use of primary articles as source material. Examples of secondary sources include: review articles, systematic reviews, and meta-analyses. Other sources, such as practice guidelines and expert topic summaries are usually considered secondary as well (although some would argue that they are tertiary since they reference both primary and secondary sources). Secondary sources, especially systematic reviews, are written under specific guidelines and protocols and often include methods sections and abstracts. So the presence of these sections are not necessarily an indication of a primary source. Many secondary sources that are published in peer-reviewed journals will also include an abstract, although many are not structured abstracts and if they are, often contain different section headers.


Categorize the example articles linked below. Open the PubMed record, review the abstract, then skim the full text on the journal website. Once you have decided whether it is primary or secondary literature, click on "more..." below the article link to find the answer.

Get Help

Have more questions? Ask a librarian!

If you are not sure if something is a primary or secondary source, contact one of our librarians using the links on the left.