case study
Published: 20 April 2021

Creating an internationally registered and fully accessible search strategy code for systematic reviews

Dr Eirini Martinou, Clinical Research Fellow in Hepato-Pancreato-Biliary (HPB) Surgery, and Dr Angeliki Angelidi, Post-Doctoral Research Fellow in Diabetes have been addressing issues researchers experience designing and performing search algorithms that are PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) compliant.

Eirini Martinou

The issue

Systematic reviews (SRs) present an unbiased, comprehensive picture of all the available evidence that can be used to drive practice in healthcare and in other disciplines (Higgins, J. et al, 2021). To perform a PRISMA-compliant SR, a meticulous search strategy is crucial (Liberati, A. et al, 2009). A methodological limitation researchers face is the lack of practical guidance on how to design and perform an appropriate search algorithm.

There are three main issues researchers face in developing a search strategy code:

  1. The identification of appropriate controlled vocabulary. Medical subject headings (MeSH) should include all relevant synonyms or spelling variants (Lefebvre, C. et al).
  2. All possible combinations of keyword categories should be used (e.g. an SR on HOX genes and colorectal cancer would need MeSH related to ‘HOX,’ ‘colorectal’ and ‘cancer’ input) but performing a manual combination is an extremely laborious process.
  3. Vocabulary controlled terms identified in PubMed are not identical with other databases, meaning that the initial algorithm needs to be customised to meet each database’s format.

The solution

We wanted to create a certified and internationally registered search code which is easily accessible, replicable, reproducible, and modifiable by researchers worldwide.

To do so, we approached each of the three issues and came up with the following solutions:

  1. For each keyword selected, we used PubMed’s advanced search tool and MeSH Descriptor Data 2020.
  2. We designed a search code where each keyword was followed by the code [tiab] or [MeSH], all keywords were connected by the ‘OR’ operator and each keyword category was assigned a number. The search code for each term category was copied and pasted from Microsoft Word in the PubMed advanced search section and all categories were combined using the final code: #1 AND #2 AND #3.
  3. We designed search codes for Embase, Web of Science and Cochrane.

To make our research methodology transparent, we also registered our SR in the International Prospective Register of Systematic Reviews (PROSPERO).

The outcome

Creating an internationally registered and fully accessible SR search code provides an easily findable and fully accessible search strategy template that can be used, reproduced and modified by researchers worldwide. More studies need to implement open research principles to make research transparent, easily accessible and reproducible.

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Higgins, J., Thomas, J., Chandler, J., Cumpston, M., Li, T. and Page, M. Analysing data and undertaking meta-analyses. Cochrane Handbook for Systematic Reviews of Interventions. Available at [Accessed 15 April 2021].

Liberati, A., Altman, DG., Tetzlaff, J., Mulrow, C., Gøtzsche, PC., Ioannidis, JPA. et al. (2009) The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration. Journal of Clinical Epidemiology, 62(10), pp. 1-34.

Lefebvre, C., Glanville, J., Briscoe, S., Littlewood, A., Marshall, C., Metzendorf, MI. et al. Searching for and selecting studies. Cochrane Handbook for Systematic Reviews of Interventions. Available at [Accessed 15 April 2021].

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