PRISMA flow diagram mistakes to avoid
Updated 2026-10-12
Most problems with a PRISMA flow diagram are small, but peer reviewers spot them quickly. Here are ten common errors, why each one matters and how to fix it before you submit.
1. The numbers do not add up
This is the error reviewers find first. Each box should equal the box above it minus whatever left the flow at that step. Records identified minus records removed gives records screened, and so on down the page. Fix: recalculate every step from your screening log, not from memory. The worked example shows each subtraction.
2. Mixing up records, reports and studies
A record is a title or abstract in a database. A report is a document you read in full. A study is the underlying investigation, which may have several reports. Using "studies" all the way down the diagram makes the counts impossible to follow. Fix: count records at the top, reports in the middle, and give both studies and reports in the final box. The systematic review guide explains the three terms.
3. One total for all databases
PRISMA 2020 asks for the number of records from each database or register searched, where feasible. A single combined figure hides where the evidence came from and makes the search harder to reproduce. Fix: name each source and give its own count, for example MEDLINE, Embase and CENTRAL on separate lines.
4. No reasons for full-text exclusions
"Reports excluded (n = 64)" with nothing else does not meet the guideline. Readers need to see why reports were rejected to judge whether the criteria were applied fairly. Fix: list each reason with its own count, and make sure the counts sum to the total.
5. Counting a report under two reasons
A report can fail on population and on outcome at once. If you count it under both, the reasons add up to more than the number of reports excluded. Fix: put your reasons in a fixed order and record only the first one that applies.
6. Leaving out reports that could not be retrieved
Some full texts cannot be obtained: the journal is unavailable, the abstract was never published in full, or the authors do not reply. These are not exclusions on eligibility and PRISMA 2020 gives them their own box. Fix: report them under "reports not retrieved", even when the number is zero.
7. Using the 2009 layout
The older diagram with four phases and a meta-analysis box is still widely copied from earlier papers. Journals that follow PRISMA expect the 2020 version. Fix: rebuild the figure on the current layout. See PRISMA 2020 vs 2009 for how to convert it.
8. Choosing the wrong template
There are four PRISMA 2020 templates. If you searched websites or checked reference lists but used the databases-only version, those records have nowhere to go. If you updated an earlier review but used the new-review version, the previously included studies disappear. Fix: pick the template that matches your methods; for updates see the updated review guide.
9. The diagram disagrees with the text
The number of included studies in the abstract, the results section, the tables and the diagram must all match. They often drift apart after a late change or a search update. Fix: after any change, check the figure against the abstract and the first paragraph of the results.
10. A figure that is hard to read
Screenshots, stretched images and tiny text in crowded boxes all make a correct diagram look careless. Fix: export a proper image file, resize it from the corner so it keeps its proportions, and shorten long labels. The Word guide covers inserting it cleanly.
Checklist before you submit
- Every step reconciles with the step above it.
- Each database and register is named with its own count.
- Duplicates, automation-tool removals and other removals are reported separately.
- Reports not retrieved are shown.
- Every full-text exclusion reason has a count, and the counts sum to the total.
- The final box gives studies and reports.
- The included-studies number matches the abstract, results and tables.
- The figure has a caption and cites the PRISMA 2020 statement.
The generator shows a running total of the records identified across your databases and registers as you type, which gives you the starting number to check every later box against.
Quick answers
What is the most common PRISMA flow diagram mistake?
Numbers that do not reconcile from one box to the next, usually because records, reports and studies were mixed up or a late change was not carried through.
Should I show a box when the count is zero?
Yes. Keep the box and report n = 0. It shows the step was considered, for example that no reports were unretrievable.
Can I change the wording of the boxes?
You can adapt labels to fit your review, such as naming your databases or using sources of evidence in a scoping review. Keep the structure and the order of the boxes.
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.