What is a PRISMA flow diagram?
Updated 2026-10-27
A PRISMA flow diagram is a standard chart that shows how many records a systematic review found, screened, excluded and finally included. It is the visual summary of your study selection process.
The short definition
PRISMA stands for Preferred Reporting Items for Systematic reviews and Meta-Analyses. The PRISMA flow diagram is the figure that reports the journey of every record in your review, from the first database search to the studies you analysed. Readers can see at a glance how large the search was, how many duplicates were removed, how many reports were read in full and why studies were excluded.
What the diagram shows
A PRISMA 2020 flow diagram is organised in three bands:
- Identification: records found in databases and registers (and through other methods such as websites or citation searching), and records removed before screening, such as duplicates.
- Screening: records screened by title and abstract, records excluded, reports sought for retrieval, reports that could not be retrieved, reports assessed for eligibility and reports excluded with reasons.
- Included: the final number of studies and reports included in the review.
Why the PRISMA flow diagram is important
It makes your review transparent and reproducible. A reviewer can check that your numbers add up, and other researchers can see whether your search was broad enough to trust. Most journals that publish systematic reviews expect it, and it supports item 16a of the PRISMA 2020 checklist, which asks you to describe the search and selection results, ideally using a flow diagram.
PRISMA 2020 vs 2009 flow diagram
The PRISMA flow diagram was redesigned when the guideline was updated in 2020. If you learned the older layout, or you're updating a review that used it, these are the differences that matter.
The short version
- The 2009 diagram had four phases: Identification, Screening, Eligibility and Included. The 2020 diagram has three sections: Identification, Screening and Included.
- PRISMA 2020 separates records, reports and studies. The 2009 diagram used "records" and "full-text articles" and didn't distinguish a study from the papers that report it.
- Searches of databases and registers are now shown separately from other methods such as websites, organisations and citation searching.
- There are new boxes for records removed by automation tools and for reports that couldn't be retrieved.
- The separate boxes for qualitative synthesis and quantitative synthesis (meta-analysis) are gone.
- 2009 had one template. 2020 has four, including two for updated reviews.
Box-by-box comparison
| Stage | PRISMA 2009 | PRISMA 2020 |
|---|---|---|
| Search results | Records identified through database searching | Records identified from databases and from registers, ideally with a count for each one |
| Other sources | Additional records identified through other sources, as one number | A separate column for websites, organisations, citation searching and similar methods, with its own retrieval and eligibility boxes |
| Before screening | Records after duplicates removed | Records removed before screening: duplicates, records marked ineligible by automation tools, and other reasons |
| Title and abstract | Records screened; records excluded | Records screened; records excluded |
| Retrieval | Not shown | Reports sought for retrieval; reports not retrieved |
| Full text | Full-text articles assessed for eligibility; full-text articles excluded, with reasons | Reports assessed for eligibility; reports excluded, with a count for each reason |
| Included | Studies included in qualitative synthesis; studies included in quantitative synthesis (meta-analysis) | Studies included in review; reports of included studies |
| Updates | No dedicated layout | A "previous studies" column and totals for new and previous studies |
Why the diagram changed
Review methods moved on between 2009 and 2020. Reviewers now routinely search trial registers, use software to help with screening, and find evidence through citation tracking and websites. The 2009 layout had nowhere to show any of that. It also hid a real source of confusion: a single trial is often reported in several papers, so "articles" and "studies" are different counts. The 2020 diagram makes each of those visible. The full reasoning is in the PRISMA 2020 statement (Page et al., BMJ 2021;372:n71), which replaced the 2009 statement (Moher et al., PLoS Medicine 2009;6(7):e1000097).
Which version should you use?
Use the PRISMA 2020 flow diagram for any review you're writing now. Most journals that endorse PRISMA expect the current version, and peer reviewers do check. Only use the 2009 diagram if a protocol or journal instruction explicitly names it. If you're updating a review that was first published with a 2009 diagram, report the update with the PRISMA 2020 updated review template.
How to convert a 2009 diagram to PRISMA 2020
- Split the search results. Go back to your search log and get the count for each database and register, instead of one combined number.
- Separate other sources. Move records from websites, organisations and citation searching into the other-methods column. If you had none, use the databases-and-registers-only template.
- Turn "records after duplicates removed" around. The 2020 box reports how many were removed, not how many were left. Subtract to get the duplicates removed.
- Add retrieval. Count the full texts you tried to get and the ones you couldn't obtain. In 2009 these were often folded into the exclusions.
- Rename full-text articles as reports and keep a count for each exclusion reason.
- Replace the two synthesis boxes. Give the number of studies included and the number of reports of those studies.
Then check that each box reconciles with the one above it. The worked examples show the arithmetic, and the generator lays out the 2020 boxes for you once the numbers are in.
Where it goes in your paper
The diagram is normally Figure 1 and is cited in the Results section, in the paragraph that describes study selection. Add a short sentence with the key numbers, then refer readers to the figure for the full detail.
Next steps
Ready to draw yours? Read how to make a PRISMA flow diagram, look at a worked example, or open the free PRISMA flow diagram generator and start filling in your numbers.
Quick answers
What does PRISMA stand for?
PRISMA stands for Preferred Reporting Items for Systematic reviews and Meta-Analyses.
Is a PRISMA flow diagram required?
The PRISMA 2020 checklist recommends a flow diagram for reporting study selection, and most journals publishing systematic reviews expect one.
Why is a PRISMA flow diagram important?
It makes study selection transparent and easy to check: readers can see how many records each search produced, how duplicates were removed, and why studies were excluded. PRISMA 2020 checklist item 16a asks reviews to report this, ideally with a flow diagram, and most journals expect one.
Can I still use the PRISMA 2009 flow diagram?
Only if your journal or protocol specifically asks for it. For new reviews, use PRISMA 2020, which replaced the 2009 version.
Where did the meta-analysis box go?
PRISMA 2020 removed the separate qualitative and quantitative synthesis boxes. The final box reports the studies included in the review. If only some were pooled in a meta-analysis, give that number in your results text.
Source of the flow diagram wording: Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71. doi:10.1136/bmj.n71. Licensed CC BY 4.0. This site is independent and not affiliated with the PRISMA or EQUATOR Network groups.