PRISMA Flow Diagram Explained: A Practical Guide for Systematic Reviews

A PRISMA flow diagram summarizes how a review moved from identified records to included studies. This tutorial shows how to select a template, distinguish records, reports and studies, and reconcile each count with the underlying search and selection log. Keep the actual decisions and retrieval records beside the diagram: a final reference list cannot reconstruct that history.

What is PRISMA? (History and Purpose)

PRISMA stands for Preferred Reporting Items for Systematic reviews and Meta-Analyses. The 2009 statement introduced a checklist and flow diagram to improve reporting. The PRISMA 2020 statement, published in 2021, updates that reporting guidance and distinguishes records, reports and studies more clearly. A completed diagram documents the selection process; it does not establish that the review methods were appropriate.

Choose an official PRISMA 2020 template for a new or updated review, with either databases and registers alone or additional identification methods. The PRISMA 2020 materials are available under CC BY 4.0. When adapting a diagram, acknowledge its source, link the license and identify your changes.

If you are still choosing the reporting documents for your review, start with the PRISMA reporting guide.

The PRISMA Flow Diagram: Phases and Boxes

The branches describe how evidence was identified. Database and register searches belong in that branch. Other methods include searching websites and organizations, checking references and citation searching. These are not separate branches for published and grey literature: a report’s publication status does not determine how it was found. Select the template that matches your actual process.

• Identification: Record the records found through each source and the records removed before screening. Keep source exports and duplicate decisions so the totals can be checked.
• Screening: Count records screened and excluded at title/abstract screening. The records taken forward lead to reports sought for retrieval.
• Retrieval and eligibility: A report is a document supplying information about a study. Record attempts to obtain reports, retrieval failures and the retrieved reports assessed for eligibility as distinct stages.
• Inclusion: Report both unique studies and reports of those studies. Two papers reporting the same trial may contribute two reports but only one study.

Follow the arrows in the selected template and keep a log for any adapted path. Reports found by other methods still need an eligibility decision. Do not move them directly into the final study count simply because they were identified outside a database.

PRISMA flow diagram generator

Differences: PRISMA 2009 vs PRISMA 2020

Use the 2020 template that matches your review instead of trying to force every review into two columns. Report source-level detail in the search log or supplement when the diagram displays totals. The additional boxes help readers follow the process, but the underlying records remain necessary.

Step-by-Step Walkthrough of the PRISMA Flow

1. Identify records. Record each search source and export count before deduplication. Log records identified through other methods as well, with enough detail to explain what was actually inspected.
2. Remove duplicates and other pre-screening removals. Keep the reason for each removal. Duplicate records are different from multiple reports of one study.
3. Screen titles and abstracts. Apply the documented criteria and record the number screened and excluded. Keep uncertain records for clarification or retrieval according to the protocol.
4. Retrieve reports. Reports sought for retrieval are the reports you tried to obtain after screening. Reports not retrieved are those you could not obtain. Reports assessed for eligibility are the retrieved reports that reached the eligibility assessment. Keep retrieval failures separate from reports excluded after assessment; the latter need recorded eligibility reasons.
5. Assess eligibility. Apply the review criteria to the reports obtained, record exclusions with reasons and reconcile those counts with the diagram. A missing usable result for one analysis is not automatically a reason to exclude the study from the review.
6. Link reports to studies. Assign study identifiers before producing the final totals. Include all relevant reports of an included study in the mapping, even when only one supplies an analysis result.

These counts are invented for teaching. In this example, the exclusion reasons are mutually exclusive primary reasons. In a real review, derive the study count from the report-to-study mapping, and resolve overlap between sources before combining branches.

The image and Word download above show the official template for a new review using databases and registers. They are blank templates, separate from the fictional counts in the worked example. Choose a different official template when other identification methods or a previous review need to be represented.

Common Mistakes and Pitfalls

• Missing other-methods records: Preserve what was found and assessed through websites, organizations and citation searching. Do not report only the records that eventually qualified. Explain any practical limit on what could be inspected.
• Confusing a source with a method: For example, a citation index can support a topic search or citation searching. Describe the method and apply the chosen flow structure consistently.
• Using a displayed hit estimate as an export count: For web search tools, distinguish the displayed estimate from records you could access, export and screen. Record the actual procedure and stopping rule rather than assuming a universal result cap.
• Counting reports as studies: Check every included report against its study identifier. A discrepancy between report and study totals may be correct, but it must be explained by the mapping.
• Losing search updates: Retain each search run and date, reconcile overlap with earlier runs and explain how the combined counts were obtained. An updated published review also needs the appropriate updated-review template.

Practical Tips for Creating Your PRISMA Diagram

• Use the matching official template. The PRISMA flow-diagram page provides Word templates and links to diagram tools. Check the resulting boxes against your own records.
• Credit adaptations. Acknowledge PRISMA 2020, link CC BY 4.0 and identify changes when adapting the diagram.
• Retain the supporting logs. Include exact search strategies, source counts, retrieval outcomes and report-to-study links in an inspectable supplement where appropriate. A screenshot alone does not replace an exact query.
• Check the correct reporting items. PRISMA 2020 item 16a concerns the results of search and selection. Item 16b concerns citing apparently eligible studies that were excluded and explaining why. Keep the flow diagram and exclusion record consistent. Item 7 concerns search strategies; it is not the exclusion-list item.

Key Takeaways

• Select the template for your review status and identification methods.
• Keep records, reports and studies distinct throughout the log.
• Separate reports sought, reports not retrieved and reports assessed.
• Reconcile exclusions with recorded reasons and study totals with report-to-study links.
• Keep the source records beside the diagram so another reader can follow the counts.