Literature reviews written to PRISMA 2020 standards.
Systematic, scoping and narrative reviews for medical research. Reproducible database searches, dual screening, risk-of-bias assessment and a PRISMA flow diagram that stands up to peer review.
What a literature review involves
A literature review can mean very different things: a narrative overview in a thesis chapter, a scoping review mapping the field, a full systematic review with meta-analysis, or an umbrella review of reviews. Each has its own protocol, rigor requirement and reporting standard. Mixing them up is the most common reason a review does not survive peer review.
We work across all four types, with the bulk of our work on PRISMA 2020-compliant systematic reviews and scoping reviews following PRISMA-ScR. Every systematic review begins with a registered protocol (PROSPERO for most clinical questions), a reproducible search strategy across at least two bibliographic databases plus grey literature, dual screening against pre-specified eligibility criteria, and risk-of-bias assessment using a design-appropriate tool.
For narrative reviews in thesis chapters or invited perspective articles, we apply the same search discipline to a less rigid synthesis - the goal there is depth of argument rather than exhaustive coverage. Either way, the search is documented so that another researcher could reproduce it.
What changed from 2009.
PRISMA 2020, published in 2021, supersedes the 2009 statement. The main checklist keeps 27 top-level items but restructures them and adds sub-items for clarity. A new 12-item PRISMA-for-Abstracts checklist accompanies it, along with an updated flow diagram.
The revision adds explicit guidance on reporting search strategies across databases and registers, plus new items for data availability, risk-of-bias synthesis, and certainty-of-evidence (GRADE).
Every systematic and scoping review we draft follows PRISMA 2020. Legacy reviews that referenced the 2009 statement are flagged in the methods write-up so reviewers see the change explicitly.
Review types we cover
- Systematic reviews with or without meta-analysis (PRISMA 2020)
- Scoping reviews (PRISMA-ScR)
- Rapid reviews under tight timelines with acknowledged methodological shortcuts
- Narrative reviews for thesis chapters and invited articles
- Umbrella reviews synthesising existing systematic reviews
- Protocol writing and PROSPERO registration
- Search strategy development across PubMed, Embase, Scopus, Cochrane CENTRAL, CINAHL, Web of Science
- Grey literature searches including trial registries (CTRI, ClinicalTrials.gov, WHO ICTRP)
- Dual screening at title-abstract and full-text stages with conflict resolution
- Risk-of-bias assessment: RoB 2 for RCTs, ROBINS-I for non-randomised, QUADAS-2 for diagnostic accuracy, Newcastle-Ottawa for observational
- Meta-analysis in R (metafor) or STATA (metan); heterogeneity, subgroup and sensitivity analysis
- GRADE assessment of certainty of evidence
How we work on a review
- 01
Question framing with PICO or PICOS
We frame the review question using PICO (Population, Intervention, Comparison, Outcome) or PICOS (adding Study design) so eligibility criteria can be written unambiguously. For scoping reviews we use PCC (Population, Concept, Context). The eligibility criteria drive everything that follows.
- 02
Protocol and registration
For systematic reviews we draft the protocol and register it in PROSPERO (or OSF for scoping reviews) before screening starts. The protocol specifies databases, search dates, eligibility, screening procedure, data extraction fields, risk-of-bias tool and synthesis plan.
- 03
Search strategy
We build a search strategy with controlled vocabulary (MeSH, Emtree) and free-text terms, validated against a small set of known-relevant papers. The strategy is adapted and run across at least two databases, supplemented with hand-searching of reference lists and grey literature. Every search is documented with date, database, search string and yield.
- 04
Screening and extraction
Title-abstract and full-text screening are run by two reviewers independently in Rayyan, Covidence or an equivalent tool, with disagreements resolved by discussion or a third reviewer. Data extraction uses a piloted extraction form; risk of bias is assessed using the design-appropriate tool.
- 05
Synthesis and reporting
Quantitative synthesis (meta-analysis) or narrative synthesis is written against the PRISMA 2020 checklist and flow diagram. Heterogeneity is quantified (I-squared, tau-squared), sources explored with subgroup or meta-regression, and certainty of evidence rated with GRADE. The final manuscript includes the full search strategy as a supplement.
What you get
- Review protocol, registered with PROSPERO (for systematic reviews) or OSF (for scoping reviews)
- Documented search strategy for every database, with dates, strings and yields
- Completed screening records in Rayyan/Covidence with inter-rater agreement (kappa) statistics
- Data extraction workbook with all included studies coded against the protocol
- Risk-of-bias assessment using the design-appropriate tool (RoB 2, ROBINS-I, QUADAS-2, etc.)
- Meta-analysis forest plots, funnel plots and heterogeneity statistics (where quantitative synthesis is performed)
- PRISMA 2020 flow diagram and completed 27-item checklist
- Final manuscript ready for submission to the target journal
Standards we follow
27-item main checklist, 12-item abstract checklist, and updated flow diagrams for original and updated reviews.
22-item extension used when the review goal is mapping rather than synthesising evidence for an effect.
Methodological bible for Cochrane-style systematic reviews; widely applied beyond Cochrane as well.
16-item critical appraisal tool for systematic reviews; we use it as a quality check against our own work.
Cochrane's current RoB tool for RCTs included in meta-analyses.
Framework for rating certainty of the body of evidence across studies; expected by most medical journals.
Common questions about literature reviews
How is PRISMA 2020 different from the older PRISMA statement?
PRISMA 2020 replaced the 2009 statement with an expanded 27-item main checklist (up from 27 items in a different arrangement), a new 12-item abstract checklist, and revised flow diagrams that distinguish original reviews from updates. The methodological bar also shifted: PRISMA 2020 expects reporting on protocol registration, certainty-of-evidence assessment (GRADE), and detailed search documentation in a way the 2009 version did not make mandatory. Reviews published after 2021 are increasingly expected to meet PRISMA 2020.
How many databases do I need to search?
For most clinical topics the minimum is two bibliographic databases - usually PubMed/MEDLINE and Embase - supplemented with Cochrane CENTRAL when randomised trials are relevant. Scoping reviews sometimes work with a single database plus grey literature; high-impact systematic reviews may search four to six databases plus trial registries. We advise based on the question, the journal you are targeting, and the scoping search yields. Peer reviewers often ask why a particular database was excluded, so the rationale must be documented.
Do you run dual screening, or is one reviewer enough?
Dual independent screening at both title-abstract and full-text stages is a PRISMA 2020 expectation and a Cochrane requirement. We run it in Rayyan or Covidence, with a second reviewer (us or a member of your team) and a third for conflict resolution. We also report inter-rater agreement (Cohen's kappa) in the methods. Single-reviewer screening is acceptable for certain rapid reviews but must be declared, and most medical journals will question it.
Which risk-of-bias tool should my review use?
It depends on study design. For RCTs, Cochrane's RoB 2 (which superseded RoB 1 in 2019). For non-randomised interventional studies, ROBINS-I. For diagnostic accuracy, QUADAS-2. For observational studies, Newcastle-Ottawa is commonly accepted though methodologically contested. For prevalence studies, JBI's checklist. The tool must match the design; using a single tool across mixed designs is a common reviewer critique.
Can you handle the meta-analysis if my review ends up quantitative?
Yes. We run meta-analyses in R (metafor, meta packages) or STATA (metan, metareg) with full documentation of effect measure choice, fixed vs random effects, heterogeneity quantification (I-squared, tau-squared, prediction intervals), subgroup and sensitivity analyses, and publication-bias assessment (funnel plot, Egger's test where appropriate). Scripts and output are shared so the analysis is reproducible for peer review.
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Study design, sample size, hypothesis testing, regression and survival analysis for medical research.
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Gap analysis against recent literature, feasibility scoring against your specialty, timeframe and institutional resources, and a shortlist your guide can sign off on.
Read moreWhat we don't do.
No ghost-authorship
Your name, your voice, your work. We do not put our names on your thesis or paper.
No publication guarantees
Peer review is not ours to promise. We make the work stronger; the journal decides.
No fixed turnaround promises
Good research takes the time it takes. We scope honestly, not optimistically.
No shortcuts
No AI paraphrasing to game similarity checks. No plagiarism. No sentence-swapping.
Talk to us about your project.
Send over an abstract, a chapter or a rough outline of what you need. We reply within one working day with a clear scope and a fixed quote, no obligation to proceed.