Systematic Literature Review
A reproducible, PRISMA 2020-compliant review — protocol, screening, appraisal and synthesis.
A systematic review is not a longer literature review. It is a study in its own right, with a method that someone else should be able to repeat and reach the same set of papers: a question fixed in advance, a protocol, documented searches across several databases, two people screening independently, a formal appraisal of each study’s risk of bias, and a synthesis whose limits are stated. Journals increasingly check that a review labelled “systematic” follows this full method, beyond including a flow diagram.
Most scholars reach us at one of three stages. Some need a systematic review as a thesis chapter or a first publication and want to plan it properly. Some have started, have a few thousand records in a spreadsheet, and are unsure how to screen them defensibly. And some have finished screening and are stuck on appraisal, data extraction or whether a meta-analysis is even possible.
We work to the PRISMA 2020 reporting guideline (the 27-item checklist and flow diagram published by Page and colleagues in 2021) and the methods guidance in resources such as the Cochrane Handbook. Two points up front. Systematic reviews take months, not weeks. And a meta-analysis is done only when the included studies are similar enough to pool; pooling dissimilar studies produces a number reviewers are likely to question. If you are doing the review yourself, our step-by-step systematic review guide covers the method.
Scope
What’s included
Each stage can be bought on its own, and most scholars need only some of them. Screening is the one stage that always includes you, because the review is yours.
Question and protocol
A focused question using PICO, PEO, SPIDER or a similar framework, eligibility criteria, planned methods and a protocol written to PRISMA-P, ready for registration on PROSPERO or OSF Registries.
Search strategy
Database-specific search strings with controlled vocabulary (MeSH, Emtree) and free-text terms for each database, a search log with dates and hit counts, and grey-literature and citation-chasing plans.
Screening set-up and support
Deduplication, a Rayyan or Covidence project, a pilot round to calibrate the criteria, and a documented process for two independent screeners with conflicts resolved and agreement reported.
Data extraction and risk of bias
A piloted extraction form, and appraisal with the tool that fits your study designs: RoB 2 for randomised trials, ROBINS-I for non-randomised studies, or CASP and JBI checklists for qualitative and other designs.
Synthesis and meta-analysis
Narrative synthesis structured by outcome or theme, or, where studies are comparable, a meta-analysis with heterogeneity assessment, sensitivity analyses and reproducible R or RevMan files.
PRISMA reporting review
A check of your manuscript or chapter against the full PRISMA 2020 checklist, a correctly counted flow diagram, and the completed checklist with page numbers for journal submission.
Quality
How quality is verified
These are the checks every piece of work goes through before it reaches you.
Search strings re-run before reporting
We re-run every search string in each database, confirm the hit counts in the log, and record the final search date. The most common PRISMA discrepancy is a count that can’t be reproduced.
Flow diagram numbers reconciled
Every box in the PRISMA flow diagram is checked arithmetically against the screening export, with reasons recorded for every full-text exclusion.
Screening agreement measured
After the pilot round we calculate agreement between screeners (for example Cohen’s kappa) and refine the criteria before full screening, rather than discovering the inconsistency afterwards.
Right appraisal tool for each design
We match the risk-of-bias tool to the study design and document each judgement with the supporting text, so an assessment can be traced back to the paper.
Meta-analysis only when justified
Before pooling we check that the populations, interventions and outcome measures are comparable. If they aren’t, we tell you, and structure a narrative synthesis instead.
Completed checklist delivered
You receive the completed PRISMA 2020 checklist with the location of each item in your text, so you and the journal can verify compliance.
Time
Realistic timelines
Plan for months. Studies of published systematic reviews in health research have found them to take well over a year on average from registration to publication. A thesis-chapter review with a narrow question can be quicker, though it is still usually a matter of months.
| Stage | Typical time | What it depends on |
|---|---|---|
| Question and protocol | 2–3 weeks | How settled the question is; supervisor sign-off |
| Registration (PROSPERO, where eligible) | Several weeks, sometimes longer | The registry’s own processing, which is outside our control |
| Search strategy and running searches | 2–4 weeks | Number of databases and complexity of the topic |
| Title and abstract screening | 3–8 weeks | Number of records (often 2,000 to 10,000) |
| Full-text screening | 2–6 weeks | Number of full texts and how easily they can be obtained |
| Extraction and risk of bias | 3–8 weeks | Number of included studies and complexity of outcomes |
| Synthesis, meta-analysis and write-up | 4–8 weeks | Whether pooling is possible; revision rounds with you |
Before you search
Registration: PROSPERO, OSF or neither?
Registration is expected by many journals and is good practice, but not every review is eligible for every registry.
PROSPERO registers systematic reviews with an outcome of direct relevance to human health, including many reviews in medicine, nursing, public health, psychology and allied fields. It does not accept scoping reviews or literature reviews that are not systematic, and it expects you to register before screening begins. A review that has already finished extraction may be refused. Reviews in management, education, engineering or computer science usually fall outside its scope.
For those, OSF Registries accepts pre-registered protocols from any discipline, free of charge, and gives you a time-stamped public record. Alternatively, a protocol can be published as a paper in a protocol journal. The point in every case is the same: showing that your question and methods were fixed before you saw the results.
Systematic review, scoping review or narrative review?
If your question is about what research exists on a broad topic rather than what the evidence shows about a specific effect, a scoping review (reported to PRISMA-ScR) may be the accurate label. If your department just needs a thorough, argued thesis chapter, a well-documented narrative review is usually enough; see our literature review writing support. We’ll tell you at the consultation which one fits; a label that matches the method helps the paper through editorial screening.
When a meta-analysis makes sense
A meta-analysis needs at least a few studies measuring comparable outcomes in comparable populations, with the effect sizes and variances reported or obtainable. When those conditions hold we run it with random-effects or fixed-effect models as appropriate, report heterogeneity (such as I²), and check small-study effects where there are enough studies to do so. When they don’t, a narrative synthesis is used instead. For deeper statistical work around the review, see our statistical analysis service.
Pricing
How pricing works
Systematic reviews vary hugely in size: a narrow question may yield 800 records and 12 included studies, a broad one 9,000 records and 80. We quote only after seeing your question, a draft protocol if you have one, and a rough idea of the evidence base. The quote is fixed for the stages you choose and agreed in writing before work begins.
Where the size of screening cannot be known in advance, we quote the protocol and search stages first, then quote screening once the real record count is in front of both of us, so the price reflects the actual work.
What the quote depends on
- Which stages you need
- Number of records returned and studies included
- Number of databases and complexity of search strings
- Study designs involved and the appraisal tools they need
- Whether a meta-analysis is feasible and required
Every quote includes
- A written scope listing exactly what will be delivered
- A fixed price agreed before any payment
- Payment in stages, tied to delivery
- Revision rounds stated in the scope
Process
How it works
Free consultation
A call or message with a specialist in your subject. We review your material and say plainly whether we are the right fit.
Written scope and quote
You get a written scope, a timeline and a fixed price. Work and payment begin once you agree to it.
Staged delivery
Work arrives in stages you review, each with a similarity report where text is involved. You pay stage by stage.
Revisions and hand-over
Revision rounds are included. At the end you get the final files, and an explanation of anything you’ll need to defend.
Keep reading
Guides and related services
How to do a systematic review: the PRISMA 2020 steps
The PRISMA 2020 steps from protocol to flow diagram, for a PhD chapter or a standalone paper.
How to write a literature review
How to move from summarising papers to building an argument that ends at your research gap.
Literature Review Writing
A review that synthesises and argues toward your gap, rather than summarising paper after paper.
Writing a research gap statement
The kinds of gap, a sentence pattern that works, and weak-versus-strong examples.
FAQ
Frequently asked questions
Can a systematic review be done in a month?
Usually not. Protocol, searching, dual screening, appraisal and synthesis each take weeks, and PRISMA asks you to report every one of them. A tightly scoped rapid review is possible in a shorter time, labelled as a rapid review.
Can you just do the whole review and I submit it?
You lead the review. The question, the eligibility judgements and the interpretation are yours, and the methods section describes accurately who did what. We support every stage, and can serve as a second independent screener, so you can defend the review with confidence.
Do I have to register on PROSPERO?
Only if your review is eligible and your journal or university expects it, as many health journals do. If your topic is outside PROSPERO’s health remit, OSF Registries is a common alternative. Registration should happen before screening begins, so plan it early.
I only found six studies. Can I still do a meta-analysis?
Possibly, if they measure comparable outcomes in comparable ways. But some checks, such as funnel plots for publication bias, are generally not meaningful with so few studies. Often a carefully structured narrative synthesis is more defensible. We will look at the studies and advise on which approach fits.
Rayyan or Covidence?
Both support blinded dual screening. Rayyan has a free tier and is widely used by students; Covidence is subscription-based but many institutions have licences and it also handles extraction and risk-of-bias forms. Use whichever your institution provides.
What if the examiner asks why a study was excluded?
With a proper screening record you can answer precisely: every full-text exclusion has a reason logged against it. We set up the process so that record exists and matches the flow diagram in your thesis.
Will my review idea be kept confidential?
Yes. Your question, protocol and data are shared only with the people working on your review, used only for your project, and deleted on request afterwards. We will sign an NDA if you want one.
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