A systematic review differs from a narrative one in a single word: reproducibility. Anyone should be able to follow your process and reach the same set of included studies. PRISMA is the standard that makes that possible.
1. Write a protocol first
Before searching, define your research question (often with a framework like PICO), your databases, your search strings, and your inclusion and exclusion criteria. Registering or at least documenting this protocol upfront prevents cherry-picking.
2. Search systematically
- Choose databases deliberately (Scopus, Web of Science, and field-specific ones).
- Build a Boolean search string from your key concepts and synonyms.
- Record the exact strings and the number of hits per database — you'll report these.
3. Screen in stages
- 1Remove duplicates.
- 2Screen titles and abstracts against your criteria.
- 3Assess full texts for eligibility, recording a reason for every exclusion.
- 4Arrive at your final set of included studies.
4. Draw the PRISMA flow diagram
The flow diagram visualises the four stages — Identification, Screening, Eligibility, Included — with counts at each step. It is what lets a reader (and a reviewer) audit exactly how you went from thousands of records to your final sample.
Keep a synthesis matrix as you go — one row per included study, columns for method, sample, findings and quality. Every claim in your review should trace back to a row.
5. Synthesise and report
Synthesise thematically or, where the evidence supports it, with a meta-analysis. Report against the PRISMA 2020 checklist. For end-to-end help, see our literature review mentoring.
Frequently asked
Is PRISMA mandatory for a systematic review?+
It isn't universally mandatory, but many journals require PRISMA-compliant reporting, and reviewers increasingly expect the checklist and flow diagram.
How many studies should a systematic review include?+
There is no fixed number — it depends entirely on your question and criteria. What matters is that the search and screening were exhaustive and transparent.
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