PRISMA flow diagram for a systematic review

Updated 2026-10-12

In a systematic review the PRISMA flow diagram is the standard way to report study selection. Here is what belongs in it and how to keep it defensible.

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What reviewers expect

Journals and peer reviewers look for a diagram that shows every stage from the search to the final included studies. The PRISMA 2020 checklist item 16a asks you to describe the results of the search and selection process, ideally with a flow diagram, and item 16b asks you to cite studies that might appear to meet the criteria but were excluded, and explain why.

What to include

• Number of records from each database and register, named individually.
• Records removed before screening: duplicates, records marked ineligible by automation tools, and other reasons.
• Records screened and excluded at title and abstract.
• Reports sought, not retrieved and assessed for eligibility at full text.
• Reports excluded, each with a reason and a count.
• Studies and reports included in the review.

Records, reports and studies are not the same thing

PRISMA 2020 uses three different words on purpose, and mixing them up is the most common reason a diagram does not add up.

• Record: the title or abstract (or both) of a report, as indexed in a database or on a website. This is what you screen first.
• Report: a document that gives information about a study, such as a journal article, preprint, conference abstract, register entry or dissertation. This is what you retrieve and read in full.
• Study: the investigation itself, such as one trial. A single study can be described in several reports.

So the top of the diagram counts records, the middle counts reports, and the final box gives both: the number of studies included and the number of reports they came from. If twelve trials were published across fifteen papers, the last box reads 12 studies and 15 reports.

How the numbers should reconcile

Before you submit, check each step against the one above it:

1. Records identified, minus records removed before screening, equals records screened.
2. Records screened, minus records excluded, equals reports sought for retrieval.
3. Reports sought, minus reports not retrieved, equals reports assessed for eligibility.
4. Reports assessed, minus reports excluded, equals the reports of included studies.
5. The counts for each exclusion reason add up to the total reports excluded.

The worked example runs through this arithmetic step by step.

Writing exclusion reasons

At full text, every excluded report needs one reason, and each reason needs a count. Use a short fixed list taken from your eligibility criteria, for example wrong population, wrong intervention, wrong comparator, wrong outcome and wrong study design. Decide the order in advance and record only the first reason that applies, so that no report is counted twice. Avoid a large "other" group: if it holds more than a few reports, split it into named reasons.

If you used automation tools

The box for records removed before screening has a line for records marked as ineligible by automation tools, such as a machine-learning classifier that filters out non-randomised designs. If software excluded records during screening itself, PRISMA 2020 asks you to say how many were excluded by a human and how many by the tool. Deduplication software belongs on the duplicates line, not the automation line.

Tips for a defensible diagram

Keep a log while screening so the diagram is built from data, not memory. Use the same exclusion reasons as your protocol, and order them consistently. If you updated the search, report the date of the latest search in your methods and use the updated review template if you are extending an earlier review.

Build yours

Use the free PRISMA flow diagram generator to fill in the template and export your figure, or follow the step-by-step guide. Working on a scoping review instead? See the scoping review guide.

Quick answers

Does a meta-analysis need a PRISMA flow diagram?

Yes. A meta-analysis is normally part of a systematic review, and the same PRISMA flow diagram reports its study selection.

Where does the number of studies in the meta-analysis go?

The PRISMA 2020 diagram has no separate meta-analysis box, unlike the 2009 version. If only some included studies were pooled, say so in the results text or add a line to the final box. See PRISMA 2020 vs 2009.

Do I list every database separately?

Where feasible, yes. PRISMA 2020 asks for the number of records from each database or register searched, not just the total.

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.