How to Create a PRISMA Flow Diagram for Your Systematic Review
By Dr. Zubair Khalid, DVM, MS, PhD ·
Quick Answer
- Use the PRISMA 2020 flow diagram template to document how records move through identification, screening, eligibility, and inclusion in your systematic review.
- Record the exact number of records at each stage, including duplicates removed, reports sought, and studies included, so your review is reproducible.
- The template requires honest reporting of every exclusion reason, and you must not alter numbers to fit a preferred result.
What the PRISMA Flow Diagram Does in a Systematic Review
A systematic review depends on a transparent and reproducible search and selection process. The PRISMA flow diagram is the visual record of that process. It shows how many records you identified, how many you screened, how many full reports you assessed, and how many studies you finally included. This diagram is a core part of the PRISMA 2020 statement, which is one of the reporting guidelines listed by the EQUATOR Network for transparent health research reporting.
The flow diagram serves several practical functions. It lets a reader see whether your search was broad enough to capture the relevant literature. It shows whether you applied your inclusion and exclusion criteria consistently. It also reveals whether you removed duplicate records and whether you retrieved full text for every record that appeared eligible. Without this diagram, a reader cannot tell how you moved from a large set of search results to a small set of included studies.
The diagram is not a decorative addition. It is a reporting requirement for many journals that follow PRISMA. When you submit a systematic review manuscript, the editor and peer reviewers will expect to see the flow diagram and a matching description in the methods section. The numbers in the diagram must match the numbers in your text, your search records, and your screening logs.
At a Glance: PRISMA Flow Diagram Components
| Component | What You Record | Common Source of Error |
|---|---|---|
| Identification | Total records from databases, registers, and other sources | Forgetting to report records from registers separately |
| Duplicates removed | Number of duplicate records removed before screening | Using automated deduplication without manual checks |
| Screening | Records screened and records excluded with reasons | Excluding records without documenting the reason |
| Eligibility | Full reports sought and assessed, with exclusion reasons | Not retrieving full text for every eligible record |
| Inclusion | Studies included in qualitative and quantitative synthesis | Mismatch between diagram numbers and final study count |
Core Principles of PRISMA 2020 Reporting
The PRISMA 2020 statement updated the earlier 2009 guidance to address common reporting problems. The EQUATOR Network hosts the full PRISMA 2020 explanation and elaboration document, which provides detailed guidance on each item. The flow diagram is one of those items, and it has a specific recommended structure.
The first principle is completeness. You must report every stage of the review process, from the initial search to the final inclusion. If you searched multiple databases, you should report the total number of records from all databases combined, and you may also report each database separately. If you used trial or study registers, you should report those records separately from database records.
The second principle is accuracy. Every number in the diagram must be traceable to your search records and screening logs. If you identified 1,200 records from databases and 50 from registers, the diagram must show those numbers. If you removed 300 duplicates, the diagram must show that number. If you excluded 800 records during title and abstract screening, the diagram must show that number and you should report the primary reason for exclusion.
The third principle is transparency about exclusions. The PRISMA 2020 flow diagram includes a specific box for reports not retrieved and a box for reports excluded with reasons. You should list the main reasons for exclusion, such as wrong population, wrong study design, or insufficient data. You do not need to list every excluded report individually in the diagram, but you should provide this detail in an appendix or supplementary file.
Practical Workflow for Building Your Flow Diagram
Step 1: Set Up Your Search Documentation Before You Search
The flow diagram is only as good as your search documentation. Before you run any searches, create a spreadsheet or log that will capture the number of records from each source. Include columns for the database name, the date of the search, the search strategy used, and the number of records retrieved. This log becomes the source of truth for the identification stage of your diagram.
Your search documentation should also include the full search strategy for each database. Many journals require this as a supplementary file. The National Library of Medicine hosts research methods resources that explain how to build and document search strategies for biomedical databases. A reproducible search strategy includes the exact terms, Boolean operators, filters, and date limits you applied.
Step 2: Run Your Searches and Record Results
Run your searches in each database and record the number of results. Save the results in a reference manager or a spreadsheet. Do not rely on memory for these numbers. Write them down immediately in your search log.
If you search multiple databases, you will likely find the same record in more than one database. The identification stage of the flow diagram asks for the total number of records identified from each source. You will remove duplicates in the next step, but the initial counts should reflect the raw results from each source.
Step 3: Remove Duplicates and Record the Count
Duplicate removal is a critical step because it affects all subsequent numbers. Most reference managers have an automated duplicate detection feature, but these tools are not perfect. You should run the automated check and then manually review the flagged duplicates to confirm that they are truly the same record.
Record the number of duplicates removed. This number goes into the flow diagram between the identification and screening stages. If you use a reference manager, keep a record of how many duplicates the software identified and how many you confirmed manually.
Step 4: Screen Titles and Abstracts
Screening is the process of applying your inclusion and exclusion criteria to the titles and abstracts of the remaining records. You should screen records against criteria that you defined before you started the review. These criteria should specify the population, intervention, comparison, outcomes, and study designs that you will include.
During screening, you will exclude many records because they clearly do not meet your criteria. Record the number of records screened and the number excluded. You should also record the primary reason for exclusion, even if you only track broad categories such as wrong population or wrong study design.
The Committee on Publication Ethics core practices emphasize the importance of accurate and honest reporting in all research outputs. This applies to screening decisions as well. If you exclude a record, you should be able to explain why.
Step 5: Retrieve Full Text for Eligible Records
After screening, you will have a set of records that appear eligible based on their titles and abstracts. The next step is to retrieve the full text of these reports. The PRISMA 2020 flow diagram asks you to report the number of reports sought for retrieval and the number that you could not retrieve.
Some full texts will be unavailable. The article may be behind a paywall that your institution cannot access, or the article may not exist in any accessible database. You should record the number of reports not retrieved and the reason. Interlibrary loan and direct author contact can sometimes resolve these gaps, but you should document your attempts.
Step 6: Assess Full Text for Eligibility
Once you have the full texts, you assess each one against your inclusion criteria. This is the eligibility stage of the flow diagram. You will exclude some reports because they do not meet your criteria when you read the full text. Common reasons include insufficient data, wrong study design, or duplicate publication of the same study.
Record the number of reports assessed for eligibility and the number excluded. For each excluded report, record the primary reason. The PRISMA 2020 flow diagram includes a box for reports excluded with reasons, and you should list the main reasons in the diagram or in a supplementary table.
Step 7: Finalize Your Included Studies
The final stage of the flow diagram is inclusion. You report the number of studies included in the review. If you perform a meta-analysis, you also report the number of studies included in the quantitative synthesis. These numbers may differ if some included studies do not provide data suitable for meta-analysis.
The number of included studies in the flow diagram must match the number of studies described in your results section. If you include 25 studies, your results section should describe 25 studies, and your references should list 25 primary study citations.
Mermaid Flowchart of the PRISMA 2020 Process
The following diagram summarizes the main stages of the PRISMA 2020 flow process. Use it as a mental model while you build your own diagram.
flowchart TD
A[Records identified from databases and registers] --> B[Records after duplicates removed]
B --> C[Records screened]
C --> D[Records excluded with reasons]
C --> E[Reports sought for retrieval]
E --> F[Reports not retrieved]
E --> G[Reports assessed for eligibility]
G --> H[Reports excluded with reasons]
G --> I[Studies included in review]
I --> J[Studies included in quantitative synthesis]Options and Tradeoffs in Flow Diagram Design
Database Records Versus Register Records
The PRISMA 2020 flow diagram has separate boxes for records identified from databases and records identified from registers. This distinction matters because registers such as clinical trial registries may contain records that are not yet published as full articles. If you search both databases and registers, you should report them separately in the identification stage.
The tradeoff is that separate reporting requires more careful record keeping. You need to know which records came from which source. If you import all search results into a single reference manager library, you should tag records by source so you can separate them later.
Automated Versus Manual Deduplication
Automated deduplication in reference managers is fast and usually effective, but it can miss duplicates or incorrectly flag distinct records as duplicates. Manual deduplication is more accurate but time consuming, especially for large search result sets.
A practical approach is to run the automated deduplication first, then manually review the flagged pairs. You should also spot check the remaining records for obvious duplicates that the software missed. Record both the automated and confirmed duplicate counts if they differ.
Single Reviewer Versus Dual Reviewer Screening
Screening by two independent reviewers reduces the risk of missing eligible studies, but it requires more time and coordination. Single reviewer screening is faster but carries a higher risk of error. Many systematic review methods recommend dual screening with disagreement resolution by a third reviewer.
If you screen with two reviewers, you should record the screening decisions for each reviewer and the process for resolving disagreements. This information belongs in your methods section and may be requested by peer reviewers.
Records and Measurements You Must Keep
The flow diagram depends on a set of records that you create during the review process. These records serve as the audit trail for every number in the diagram.
Your search log should contain the date of each search, the database searched, the full search strategy, and the number of results. Your screening log should contain the number of records screened, the number excluded, and the reasons for exclusion. Your full text log should contain the number of reports sought, the number retrieved, the number assessed, and the reasons for exclusion at the full text stage.
The National Institutes of Health data management and sharing policy expects researchers to plan for the preservation and sharing of data that underlies published results. For a systematic review, the search strategies, screening decisions, and exclusion reasons are part of that underlying data. You should plan to make these records available as supplementary files or in a data repository.
You should also keep a copy of your completed PRISMA checklist. The checklist documents where each reporting item appears in your manuscript. Peer reviewers and editors use this checklist to verify that you have reported all required elements.
Common Failure Patterns in PRISMA Flow Diagrams
Mismatch Between Diagram Numbers and Text
The most common failure is a mismatch between the numbers in the flow diagram and the numbers in the methods or results text. For example, the diagram may show 1,000 records identified, but the text says 950. This mismatch signals poor record keeping and undermines reader confidence in the review.
To avoid this failure, build the flow diagram from your search and screening logs instead of from memory. After you draft the diagram, cross check every number against your logs. Do this before you submit the manuscript.
Missing Exclusion Reasons
Another common failure is reporting the number of excluded records without providing reasons. The PRISMA 2020 flow diagram includes a box for reports excluded with reasons. If you leave this box empty or vague, reviewers will ask for the missing information.
Record exclusion reasons as you screen. Do not try to reconstruct them after the fact. Use a screening spreadsheet with a column for the exclusion reason, and use consistent categories across all records.
Forgetting Reports Not Retrieved
Some researchers omit the reports not retrieved box entirely. This omission is a reporting error because the PRISMA 2020 flow diagram specifically asks for this information. If you could not retrieve the full text of a report, you must report that fact.
Track retrieval attempts in your full text log. Record whether you obtained the full text through your institution, interlibrary loan, or direct author contact. If you could not retrieve a report, record the reason.
Including Duplicate Publications as Separate Studies
Duplicate publication occurs when the same study appears in more than one article. If you treat these duplicate publications as separate studies, you will overcount the number of included studies and bias your synthesis.
During full text assessment, check for duplicate publications by comparing author names, study dates, sample sizes, and outcome data. If you find duplicate publications, report them as one study and note the duplicate in your exclusion reasons.
Inflating or Deflating Numbers
The flow diagram must reflect what actually happened during the review. You must not adjust numbers to make the review look more comprehensive or more selective than it was. The Committee on Publication Ethics core practices treat data fabrication and falsification as serious misconduct. Accurate flow diagram numbers are part of honest reporting.
If your search returned very few records, report that number. If you excluded a large proportion of records, report that proportion. The flow diagram is a record of your process, not a marketing tool.
Quality Controls for Your Flow Diagram
Independent Verification of Numbers
Before you submit your manuscript, have a colleague or coauthor independently verify the numbers in your flow diagram against your search and screening logs. This verification step catches transcription errors and mismatches between the diagram and the text.
The verifier should check each number in the diagram against the corresponding log entry. They should also confirm that the arithmetic is correct. For example, the number of records screened should equal the number of records after duplicates removed, and the number of reports assessed for eligibility should equal the number of reports sought minus the number not retrieved.
Consistency With the PRISMA Checklist
The PRISMA 2020 checklist includes an item for the flow diagram. When you complete the checklist, you should indicate where the flow diagram appears in your manuscript and confirm that it includes all required elements. The EQUATOR Network provides access to the PRISMA 2020 checklist and the explanation and elaboration document.
Use the checklist as a quality control tool before submission. If any checklist item is not addressed, revise your manuscript or explain why the item does not apply.
Peer Review and Revision
Peer reviewers will scrutinize your flow diagram. They may ask for clarification about your search sources, your deduplication process, or your exclusion reasons. Respond to these comments with specific information from your logs.
If a reviewer identifies an error in your flow diagram, correct it and verify that the correction does not affect other parts of the manuscript. A corrected flow diagram may require corresponding changes in your methods text, results text, or supplementary files.
Limitations of the PRISMA Flow Diagram
The flow diagram is a reporting tool, not a quality assessment tool. A well constructed flow diagram does not guarantee that your systematic review is methodologically sound. It only shows that you reported your process transparently.
The diagram also does not capture every detail of the review process. It does not show the quality of your search strategy, the rigor of your screening criteria, or the risk of bias in your included studies. These elements are reported elsewhere in the manuscript.
The flow diagram is also limited by the quality of your underlying records. If your search log is incomplete or your screening decisions were not documented, the flow diagram will be inaccurate even if it looks complete. The diagram is only as reliable as the records that support it.
Regulatory and Publication Context
Systematic reviews are often used to inform clinical guidelines, policy decisions, and funding priorities. The National Institutes of Health expects grant applications to describe rigorous and reproducible methods, and a systematic review that follows PRISMA reporting standards is more likely to be viewed as credible.
Journals that follow the EQUATOR Network guidelines will expect your systematic review to include a PRISMA flow diagram and a completed checklist. Some journals require the checklist as a submission file. Others require the flow diagram to be included in the main manuscript file.
The Committee on Publication Ethics core practices address authorship, data integrity, and reporting standards. As an author of a systematic review, you are responsible for the accuracy of the flow diagram and all other reported data. If a coauthor contributed to the search or screening process, they should be listed as an author or acknowledged according to the journal's authorship policy.
Professional Escalation Criteria
You should seek additional guidance or escalate a problem when you encounter situations that you cannot resolve with standard methods.
If you cannot retrieve a large proportion of eligible full texts, consult a librarian or information specialist. They may have access to interlibrary loan services or alternative sources for the missing reports.
If you find substantial disagreement between reviewers during screening, stop and revisit your inclusion criteria. Disagreement often signals that the criteria are ambiguous. Clarify the criteria and retrain reviewers before continuing.
If you discover that your search strategy missed a key database or used incorrect terms, you may need to rerun the search and rescreen records. Do not proceed with an incomplete search. Document the correction in your methods section.
If you are uncertain about how to classify a study design or whether a report is a duplicate publication, consult a methodologist or a subject matter expert. These classification decisions affect your included study count and your synthesis results.
If you are preparing a systematic review for a regulatory submission or a funding application, consult the relevant program officer or regulatory contact early in the process. They can clarify the specific reporting requirements for your context.
Frequently Asked Questions
What is the difference between PRISMA 2020 and the older PRISMA 2009 flow diagram?
The PRISMA 2020 flow diagram separates records from databases and records from registers, and it includes a box for reports not retrieved. The 2009 version did not make these distinctions. The EQUATOR Network provides access to the current PRISMA 2020 guidance.
How do I count records when the same study appears in multiple databases?
Count the record in each database where it appears during the identification stage. After you combine records from all sources, remove duplicates and record the number removed. The screening stage starts with the number of records after duplicates are removed.
What should I do if I cannot retrieve the full text of an eligible report?
Record the report in the reports not retrieved box of the flow diagram. Attempt retrieval through your institution, interlibrary loan, or direct author contact. Document your attempts and the outcome.
Can I use a PRISMA flow diagram for a scoping review or a narrative review?
The PRISMA flow diagram was designed for systematic reviews, but adapted versions are used for scoping reviews and other evidence syntheses. Check the reporting guideline for your specific review type on the EQUATOR Network website.
How many exclusion reasons should I list in the flow diagram?
List the main reasons that account for the majority of exclusions. You do not need to list every reason in the diagram itself. Provide a full list of excluded reports with reasons in a supplementary file.
Do I need to include the PRISMA checklist with my manuscript?
Many journals require the PRISMA checklist as a submission file. Check the journal's author instructions. The EQUATOR Network provides the checklist and guidance on how to complete it.
What if my systematic review includes only qualitative studies?
The PRISMA flow diagram works for qualitative systematic reviews as well as quantitative reviews. The inclusion stage will report the number of studies included in the qualitative synthesis. If you do not perform a meta-analysis, you can omit or mark the quantitative synthesis box as not applicable.
How do I handle updates to a previously published systematic review?
When you update a systematic review, you should report the search and selection process for the update separately from the original review. The flow diagram should reflect the new search results, the new screening decisions, and the updated included study count.
Using the Evidence
| Source | Best use in this topic | Important limitation |
|---|---|---|
| Research Methods Resources | official guidance | Check the linked page for current local requirements |
| EQUATOR Network | official guidance | Check the linked page for current local requirements |
| Core Practices | official guidance | Check the linked page for current local requirements |
Related Articles
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References and Further Reading
- Research Methods Resources. National Library of Medicine.
- EQUATOR Network. EQUATOR Network.
- Core Practices. Committee on Publication Ethics.
- NIH Grants and Funding. National Institutes of Health.
- ORCID for Researchers. ORCID.
- Data Management and Sharing Policy. National Institutes of Health.
- NCBI Literature Resources. National Center for Biotechnology Information.
- PubMed. National Library of Medicine.
This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.