Key articles

Key articles should be articles that correspond as closely as possible to your research question. Ideally, these articles should also meet any inclusion criteria you have defined. For example, if you only intend to include randomized controlled trials written in English in your search, the articles you start from should meet these criteria.

If you are a Ph.D. student or researcher, you probably already know some key articles on your topic. If you are a student, you may have managed to find some relevant articles by test searching, or your supervisor may have given you some tips.

Use your key articles to find more keywords for your final search strategy by:

• Looking up the articles in the databases you intend to search and checking how they have been indexed, i.e. what subject headings they have been tagged with. Pay attention to whether several different subject headings seem to be used for the same concept.
• Check which terms the authors use for your key concepts in titles and abstracts. Words from titles and abstracts must be used when searching in free text databases, but can also be a good complement in databases with subject headings. Pay attention to synonyms and different linguistic forms.
• Then build up a search using the subject headings and/or terms from titles and abstracts that you have found. For tips on how to build your search, see our pages on search techniques.

Finally, check that your key articles are indeed captured by the search you created. Of course, if the result is not too large, you can go through all the hits and see that the articles are included. If, on the other hand, you have done a more comprehensive search, it is easier to test by creating a search that captures only your key articles and then testing it against your final search as follows:

• Do your search (A).
• Do a search (B) that captures only your key articles; in PubMed you can use PMID.
• Which of your key articles might not be captured by the search? Search B NOT A. Here you want the search result to be zero. Then you have captured all key articles.

If a key article is not found, consider what could be the possible reason. Would it be possible to add a search term to capture the article? Does a whole search block need to be removed? Sometimes it is not possible to modify the search so that all key articles are captured without the search result being too extensive.