Systematic literature search

How to carry out a systematic search for literature

Systematic searching can be condensed into the following five steps. It is recommended to document the process in order to have a sound foundation when writing the methods section in a future article or report.

1. Develop a research question

Developing a research question is the first step in a systematic search. Spend some time and explore the literature before formulating your research question. What are the themes and focus in your project?

Further reading:
Stern, C., Jordan, Z., & McArthur, A. (2014). Developing the review question and inclusion criteria. AJN The American Journal of Nursing, 114(4), 53–56. https://doi.org/10.1097/01.NAJ.0000445689.67800.86<

2. Identify the main concepts in the research question

The research question consists of several elements or concepts, and they form the basis for your search strategy. Identify the most important element, og select more elements when needed. To build a search strategy you can make a table with one column for each element.

Further reading:
Aromataris, E., & Riitano, D. (2014). Systematic reviews: Constructing a search strategy and searching for evidence. AJN The American Journal of Nursing, 114(5), 49–56. https://doi.org/10.1097/01.NAJ.0000446779.99522.f6

Bramer, W. M., de Jonge, G. B., Rethlefsen, M. L., Mast, F., & Kleijnen, J. (2018). A systematic approach to searching: An efficient and complete method to develop literature searches. Journal of the Medical Library Association: JMLA, 106(4), 531–541. https://doi.org/10.5195/jmla.2018.283

3. Find search terms for each element

The next step is to find search terms for each element. A concept can often be expressed in different terms, and it is therefore important to find the appropriate synonyms for each concept. You can use keywords and index terms in the search.

• Keywords are terms found in for example titles and abstracts of articles.
• Index terms are found in thesauri or lists of subject headings in the databases.

Fill in your search terms for each element in the table. If you choose very general search terms, the number of hits may be very high. Do some trial searches in order to test the number of results and the relevance of the results. The more elements you choose to combine in the search, the more specific search results you get. If the search is too narrow, you risk loosing relevant results. If the search is too broad, you risk getting many irrelevant results.

Further reading:
Aromataris, E., & Riitano, D. (2014). Systematic reviews: Constructing a search strategy and searching for evidence. AJN The American Journal of Nursing, 114(5), 49–56. https://doi.org/10.1097/01.NAJ.0000446779.99522.f6

4. Carry out searches in one or more databases

When you have selected your search terms, you combine these when searching in databases. You use the search operator OR within each element. The elements are combined with the search operator AND.

The video Using AND/OR to improve your searching, produced by NHI – Health Education England explain how to use AND and OR i searhes.

The HINN library subscribe to both subject specific and interdisciplinary databases. Each database gives you the opportunity to choose the field you would like to search, e.g. title, abstract or index terms. In addition, it is possible to adjust using techniques search as truncation, proximity search, and limitations like year, language and document type.

• Read more about search techniques at PhD on track.

Do not hesitate to reach out to the library for guidance or courses in database searching, or you may consult the databases’ help pages.
When you have performed searches in databases, the references may be downloaded to a reference management tool such as Endnote or Zotero for screening.

5. Use supplementary search techniques to find literature

In addition to search in databases, you can use supplementary techniques to identify relevant sources.

• Search in citation databases like Web of Science and Scopus for references and citations
• Read table of contents in relevant journals
• Reach out to experts Search for grey literature

Further reading:

Cooper, C., Booth, A., Britten, N., & Garside, R. (2017). A comparison of results of empirical studies of supplementary search techniques and recommendations in review methodology handbooks: A methodological review. Systematic Reviews, 6(1), 234. https://doi.org/10.1186/s13643-017-0625-1

Useful website about systematic reviews:

• PhD on track
• Systematic Reviews (University of Michigan Library)