A systematic review answers a focused question by finding and appraising all relevant studies with pre-set methods. A meta-analysis is the statistical pooling of those studies' results, usually done inside a systematic review. A scoping review maps how much evidence exists on a broad topic and where the gaps are, without judging effectiveness. A literature review (narrative review) summarises selected literature to build an argument, with flexible, often unreported, methods.
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Why choosing the right review type matters
"Review" covers a family of methods that differ in purpose, rigour and effort. Grant and Booth's (2009) widely cited typology analysed 14 review types, and concluded that few have prescribed, explicit methods and many are not mutually exclusive. No wonder researchers, supervisors and journal editors sometimes use the terms loosely.
The type you choose shapes everything that follows: how narrow your question must be, how many databases you search, whether you need a second reviewer, whether you assess study quality, and which reporting guideline the journal expects. Pick a systematic review when you really need a scoping review, and you will spend months trying to force a broad topic into a PICO question. Pick a narrative review when your supervisor expects a systematic one, and you may have to start again.
This guide compares the review types researchers most often confuse, explains when each one fits, and ends with a quick way to decide.
Systematic review vs meta-analysis vs scoping review vs literature review: at a glance
| Systematic review | Meta-analysis | Scoping review | Literature (narrative) review | |
|---|---|---|---|---|
| Purpose | Answer a focused question, often about effects | Combine results into one estimate | Map the extent and nature of evidence and gaps | Summarise and argue from selected literature |
| Question | Narrow, usually PICO | Same as the parent systematic review | Broad, usually PCC | Flexible |
| Protocol | Yes, ideally registered (e.g. PROSPERO) | Part of the review protocol | Yes, recommended | Rarely |
| Search | Comprehensive, several databases, reproducible | Relies on the systematic review search | Comprehensive, often including grey literature | Selective, often not reported |
| Screening | Two reviewers, explicit criteria | Uses included studies | Two reviewers, explicit criteria | Author's judgement |
| Quality appraisal | Yes (risk of bias tools) | Yes, feeds into the analysis | Not usually required | Optional and informal |
| Synthesis | Narrative and/or statistical | Statistical (pooled effect size) | Descriptive: charting, counts, themes | Narrative |
| Reporting guideline | PRISMA 2020 | PRISMA 2020 | PRISMA-ScR | None standard |
What is a systematic review?
A systematic review follows a pre-defined protocol to find, select, appraise and synthesise all the studies that answer a specific question. The defining features are transparency and reproducibility: the search strategies, eligibility criteria, screening decisions and appraisal judgements are all reported, so another team could repeat the review.
Systematic reviews are the right choice when you need to know whether something works, how well, or how accurate a test is, and you want the answer to be as free from selection bias as possible. They are reported with the PRISMA 2020 statement (Page et al., 2021), which has a 27-item checklist and a flow diagram.
- Typical question: In adults with chronic low back pain, does exercise therapy reduce pain compared with usual care?
- Needs: a narrow PICO question, a registered protocol, several databases, two independent reviewers, a design-specific risk of bias tool.
- Output: a synthesis of effects, often with a meta-analysis and a GRADE rating of the certainty of evidence (Guyatt et al., 2008).
Our step-by-step guide explains how to do a systematic review from question to PRISMA report.
What is a meta-analysis?
A meta-analysis is the statistical combination of results from two or more separate studies to produce a single, more precise estimate of an effect, such as a pooled odds ratio or mean difference. It also quantifies how much the results vary between studies (heterogeneity), which is often as informative as the average itself (Deeks et al., 2024).
Meta-analysis should sit inside a systematic review, because pooling a biased or incomplete set of studies simply produces a precise-looking biased answer. It is only appropriate when studies are similar enough in population, intervention, comparison and outcome for an average to mean something. When they are not, reviewers present a structured narrative synthesis instead.
- Adds: effect sizes, a pooled estimate with confidence interval, forest plots, heterogeneity statistics (I², τ²), subgroup and sensitivity analyses, and funnel plots.
- Does not replace: the systematic search, screening and risk of bias steps.
Read how to do a meta-analysis for the full workflow, or how to read a forest plot if you are interpreting one.
What is a scoping review?
A scoping review maps a body of literature: what kinds of studies exist, on which populations and settings, using which methods, and where the gaps are. Munn et al. (2018), writing for JBI, describe the main reasons to choose one: to identify knowledge gaps, scope a body of literature, clarify concepts, or investigate how research is conducted. Scoping reviews can also be a useful first step before a systematic review, confirming that enough relevant studies exist and refining the question.
Methodologically, scoping reviews are still rigorous. They follow a protocol, search comprehensively, and screen with explicit criteria. The main differences are a broader question (framed with PCC: Population, Concept, Context), no requirement to appraise study quality, and a descriptive rather than statistical synthesis. They are reported with PRISMA-ScR (Tricco et al., 2018), which has 20 essential items and 2 optional ones.
- Typical question: What is known about the use of telehealth for palliative care in rural settings?
- Output: charted data, counts of study types, evidence maps and gaps for future research.
Our guide on how to do a scoping review covers the Arksey and O'Malley (2005) framework and JBI methods (Peters et al., 2020) step by step.
What is a literature review (narrative review)?
A literature review, often called a narrative or traditional review, summarises and critically discusses selected research on a topic. It is the literature review chapter of a dissertation, the background section of a paper, or a stand-alone review article that develops an argument or theory.
Its strength is flexibility: it can synthesise theory, trace how a field developed, and draw connections across disciplines. Its weakness is that, without explicit search and selection methods, it is open to selection bias; readers cannot tell what was left out or why. Many universities now expect even dissertation literature reviews to report a search strategy, which moves them closer to a systematic approach.
See how to write a literature review for structure, synthesis matrices and examples.
Other review types you may meet
Integrative review
Common in nursing research, the integrative review combines studies with diverse methods, for example experimental and non-experimental research. Whittemore and Knafl's (2005) methodology paper describes it as the only review approach that allows this combination, and proposes strategies to make it rigorous.
Umbrella review (overview of reviews)
An umbrella review collects and appraises existing systematic reviews on a broad topic, rather than primary studies. It is useful when several reviews already cover related questions and decision-makers need them in one place.
Rapid review
A rapid review streamlines or omits some systematic review steps, such as limiting databases, dates or languages, or using a single screener with verification, to deliver evidence quickly. The shortcuts should be stated clearly because they increase the risk of missing studies.
Evidence and gap map
An evidence and gap map displays the available evidence as a matrix, usually interventions against outcomes, with bubbles showing how many studies exist and empty cells showing gaps. The Campbell Collaboration publishes guidance on producing them (White et al., 2020). You can build one from your own coded studies with our free evidence gap map generator.
How to choose the right review type
Work through these questions in order:
- Do you want to know whether an intervention works, or how accurate a test is? Choose a systematic review, with a meta-analysis if the studies are similar enough to pool.
- Do you want to know what evidence exists, how research has been done, or where the gaps are? Choose a scoping review, or an evidence and gap map if you want a visual matrix.
- Are there already several systematic reviews on your topic? Consider an umbrella review.
- Do you need to combine quantitative and qualitative evidence for practice, as in many nursing projects? Consider an integrative review, following a published methodology.
- Are you building an argument or theoretical background for a thesis or paper? A well-structured literature review is appropriate, ideally with a reported search strategy.
- Does a policy decision need evidence within weeks? A rapid review, with its shortcuts declared.
Topic: virtual reality for pain in children.
If you ask "Does VR distraction reduce procedural pain compared with standard care?" you need a systematic review and meta-analysis.
If you ask "How has VR been studied in paediatric pain, in which procedures and with which outcomes?" you need a scoping review.
Which review type suits a dissertation, thesis or capstone?
Students often face a practical question: which review can I realistically complete, alone, in the time I have? A few points help:
- Check what your programme calls it. Many universities ask for a "systematic literature review" at master's level but accept a single reviewer with a supervisor checking a sample. Read the handbook and marking criteria before you commit to full Cochrane-style methods.
- Be honest about the second reviewer. If no one can screen independently, say so and describe how you reduced bias, for example by having a supervisor check a random sample of decisions.
- A scoping review is not a shortcut. It usually involves more records to screen than a narrow systematic review, because the question is broader.
- Nursing capstones often use integrative reviews or evidence-based practice projects built on a PICOT question; see our guide on how to write a PICOT question.
- Doctoral theses increasingly include a full systematic or scoping review as a publishable chapter, so following PRISMA 2020 or PRISMA-ScR from the start saves rewriting later.
Common mistakes when naming or choosing a review
- Calling a narrative review "systematic" because the author searched a database. Without a protocol, explicit criteria, dual screening and appraisal, it is not a systematic review.
- Running a meta-analysis on a scoping review. Scoping reviews map evidence; they are not designed to estimate effects, and usually include studies too diverse to pool.
- Choosing a scoping review to avoid quality appraisal when the real question is about effectiveness. Reviewers and examiners notice.
- Using the wrong reporting guideline, for example PRISMA 2020 for a scoping review instead of PRISMA-ScR.
- Pooling everything in a meta-analysis regardless of clinical and methodological differences between studies.
Getting expert support
If you are unsure which review type fits your question, it is worth a short conversation with a methodologist before you write the protocol. At TimelyScholar our PhD-led team supports systematic reviews, meta-analyses, scoping reviews and literature reviews, from choosing the design to searching, screening, analysis and reporting.
Frequently asked questions
Is a meta-analysis better than a systematic review?
Neither is better; they do different jobs. A meta-analysis is a statistical step that is only meaningful inside a well-conducted systematic review, and only when the included studies are similar enough to combine.
What is the main difference between a scoping review and a systematic review?
A systematic review answers a focused question, often about effectiveness, and appraises study quality. A scoping review maps the extent and nature of evidence on a broader topic and does not usually appraise quality.
Can a literature review be systematic?
A literature review becomes a systematic review only when it follows a protocol with explicit search, screening and appraisal methods reported in full. Adding a database search alone does not make it systematic.
Which reporting guideline does each review use?
Systematic reviews and meta-analyses use PRISMA 2020. Scoping reviews use PRISMA-ScR. Narrative literature reviews have no single standard guideline.
What is an umbrella review?
An umbrella review, or overview of reviews, collects and appraises existing systematic reviews on a topic instead of primary studies.
Do scoping reviews need quality appraisal?
It is not usually required, because the aim is to map evidence rather than judge effects, although some authors choose to report it.
Sources
- Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J 2009;26:91-108
- Arksey H, O'Malley L. Scoping studies: towards a methodological framework. Int J Soc Res Methodol 2005;8:19-32
- Guyatt GH, Oxman AD, Vist GE, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ 2008;336:924-926
- Munn Z, Peters MDJ, Stern C, et al. Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach. BMC Med Res Methodol 2018;18:143
- Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71
- Tricco AC, Lillie E, Zarin W, et al. PRISMA Extension for Scoping Reviews (PRISMA-ScR): checklist and explanation. Ann Intern Med 2018;169:467-473
- Peters MDJ, Marnie C, Tricco AC, et al. Updated methodological guidance for the conduct of scoping reviews. JBI Evid Synth 2020;18:2119-2126
- Whittemore R, Knafl K. The integrative review: updated methodology. J Adv Nurs 2005;52:546-553
- Deeks JJ, Higgins JPT, Altman DG, McKenzie JE, Veroniki AA, editors. Chapter 10: Analysing data and undertaking meta-analyses. In: Higgins JPT, Thomas J, Chandler J, et al., editors. Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane; 2024
- White H, Albers B, Gaarder M, et al. Guidance for producing a Campbell evidence and gap map. Campbell Syst Rev 2020;16:e1125
Emily brings 12 years of experience in higher education. She provides senior-level oversight for complex research projects, helping teams clarify scope, align research questions with methods, and strengthen the logic and reporting of their work. Areas of expertise Oversight of institutional research and research…