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Doing the literature review: Reporting your search strategy

Reporting your search strategy

PRISMA, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, is a minimum set of items for reporting in systematic reviews and meta-analysis. Even when your goal isn't a systematic review or a meta-analysis, this set of items can also help you to search in more systematic way and to make your search more transparent and reproducable (also for your future self!).

The PRISMA 2020 Statement consists of a checklist and a flow diagram.

The checklist consists of 27 items. It guides you through the choices you have to make when you do a literature review. For example: what are criteria for eligibility (when do you include a paper or not), which databases have you used, what was the search strategy? This will make your literature review more systematic, better structured, and it will be easier to write down the steps in your paper or article. 

The flow diagram shows the ‘flow’ of information in the different phases of a systematic review, by showing the number of records identified, included and excluded, and the reasons for exclusions. In the academic literature you will find a lot of variants of the flow diagram.

In 2021, the PRISMA extension for searching was published: a checklist of 16 items to report literature searches in systematic reviews. They are more specific than the PRISMA Statement. 

Examples of the PRISMA flow diagram

In the PRISMA flow diagram you summarize the study selection process. In the diagram you report:

Identification

  • The number of records found by searching databases. You can add the number of records found in each database used.
  • The number of records found via other methods, for example via the reference lists, via citing articles, or via experts.

Screening

  • The number of records screened – this means in this stage reading the titles and abstracts.
  • The number of records excluded, because they do not meet your inclusion criteria (for example, the age group of the participants in the study doesn’t match) or fit your exclusion criteria (for example the article is in French).
  • The number of reports sought for retrieval, and the number of reports not retrieved.
  • The number of reports assessed for eligibility – and the number of reports excluded, with the reason why.

Included

  • The number of studies included in the review.

Page, M. J., McKenzie, J. E., Bossuyt, P. M., Boutron, I., Hoffmann, T. C., Mulrow, C. D., Shamseer, L., Tetzlaff, J. M., Akl, E. A., Brennan, S. E., Chou, R., Glanville, J., Grimshaw, J. M., Hróbjartsson, A., Lalu, M. M., Li, T., Loder, E. W., Mayo-Wilson, E., McDonald, S., . . . Moher, D. (2021). The PRISMA 2020 statement: An updated guideline for reporting systematic reviews. BMJ, 372, n71. https://doi.org/10.1136/bmj.n71

In the other tabs you can see examples of how the PRISMA flow diagram is applied in academic articles. 

Flow diagram as reported in Wang et al.

Source: Wang, H., Buljac-Samardzic, M., Wang, W., van Wijngaarden, J., Yuan, S., & van de Klundert, J. (2021). What do we know about teamwork in Chinese hospitals? A systematic review. Frontiers in Public Health, 9, Article 735754. https://doi.org/10.3389/fpubh.2021.735754

PRISMA Flow diagram in Scheuplein and van Harmelen (2022)

Source: Scheuplein, M., & van Harmelen, A. (2022). The importance of friendships in reducing brain responses to stress in adolescents exposed to childhood adversity: A preregistered systematic review. Current Opinion in Psychology, 45, Article 101310. 
https://doi.org/10.1016/j.copsyc.2022.101310

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