Purposes and Types of Literature Review

Overview

A literature review is a structured examination of existing knowledge relevant to a question. In a research proposal, it establishes what is known, where uncertainty remains and why a new study is needed. In a manuscript, it helps interpret findings in relation to previous evidence. A literature review can also be a research project in its own right when the aim is to identify, appraise and synthesise evidence.

The label attached to a review does not by itself establish its quality. Review terminology overlaps, and different review types vary in the breadth of their questions, search methods, appraisal procedures, synthesis methods and intended products [1]. The review approach should therefore be selected by purpose and methodological requirements rather than by perceived prestige.

Why this matters

An unfocused literature review often becomes an article-by-article summary that does not support a research decision. It may over-represent familiar authors, English-language publications, recent papers or studies with favourable findings. At the other extreme, a research team may attempt a full systematic review when the immediate need is only to understand a concept, refine a local problem or map the range of available evidence.

Choosing an appropriate review approach affects workload, team composition, search comprehensiveness, critical appraisal, reproducibility and the strength of conclusions. A review intended to estimate an intervention effect requires different methods from a review intended to clarify how a concept has been defined.

What a literature review contributes

A literature review may support several stages of a health-research project.

Defining the problem

The review establishes the burden, context and consequences of the problem. It distinguishes a genuine evidence gap from a gap created only because the researcher has not yet searched adequately.

Refining the question and objectives

Existing studies reveal how populations, exposures, interventions, outcomes and experiences have been defined. They may show that an initially broad question contains several distinct questions.

Informing design and measurement

Prior research can identify feasible study designs, validated instruments, operational definitions, follow-up intervals, recruitment barriers and known confounders. This does not mean copying methods uncritically; the local setting and intended inference still matter.

Anticipating bias, ethics and feasibility

Published limitations and protocols can alert the team to selection pathways, measurement problems, participant burden, data-access constraints and governance requirements.

Interpreting findings

A completed study should be interpreted against the totality of relevant evidence rather than against one convenient publication. Differences in population, setting, design and measurement may explain apparent inconsistency.

Background review versus evidence synthesis

A background literature review is conducted to support another research project. It should still be purposeful, traceable and balanced, but its scope may be narrower than a formal systematic review. It commonly informs the introduction, conceptual framework, methods and discussion.

A formal evidence synthesis treats the review itself as the study. It normally has a protocol, explicit eligibility criteria, a planned search, transparent selection procedures, structured appraisal and a specified synthesis method. Systematic reviews are reported using guidance such as PRISMA 2020, but PRISMA is a reporting guideline rather than a substitute for sound review methods [2].

A proposal author should not describe a few database searches as a “systematic review” unless the full design supports that label. Conversely, a background review should not be dismissed as unimportant; poor background reviewing can lead to redundant or badly designed primary research.

Common review approaches

Narrative or traditional review

DESIGN PROFILE

Narrative review

Core structure: A critical, interpretive account of selected literature organised around concepts, debates or developments.

Best suited for: Explaining a topic, integrating theory, tracing development of ideas or providing context for a proposal.

Important limitations: Selection and weighting of sources may be difficult to reproduce unless methods and boundaries are described.

A narrative review can be scholarly and analytically strong. Its value depends on the author’s expertise, breadth of reading, critical reasoning and transparency. A narrative review should not be equated with an unsystematic list of citations. Tools such as SANRA have been proposed to improve appraisal of narrative review manuscripts [3].

Integrative review

An integrative review brings together diverse forms of empirical and theoretical literature to develop a broad understanding, model or framework. It may include quantitative, qualitative and conceptual sources. Because evidence types differ, the review must explain how sources were selected, appraised and combined.

Scoping review

DESIGN PROFILE

Scoping review

Core structure: A systematic mapping of the extent, characteristics, concepts or methods within a broad body of literature.

Best suited for: Clarifying concepts, describing how research has been conducted, identifying evidence clusters and gaps, or assessing whether a later systematic review is feasible.

Important limitations: It usually does not answer a narrowly focused question about comparative effectiveness, and gap counts alone do not determine research priority.

Scoping reviews remain systematic and transparent, but their purpose differs from that of a systematic review addressing a focused effect or association. Guidance emphasises choosing a scoping approach when mapping or conceptual clarification is the objective, not merely because the literature is heterogeneous [4].

Systematic review

DESIGN PROFILE

Systematic review

Core structure: A pre-specified, reproducible process to identify, select, appraise and synthesise evidence addressing a focused question.

Best suited for: Estimating effects, describing prevalence, evaluating diagnostic accuracy, examining associations, synthesising qualitative evidence or answering another defined review question.

Important limitations: Conclusions depend on the included evidence and methods. A systematic process does not remove bias from poor primary studies or an inappropriate question.

A systematic review may or may not include meta-analysis. Meta-analysis is a statistical synthesis method, not a synonym for systematic review. Some questions require narrative, qualitative or other structured synthesis because quantitative pooling is inappropriate.

Rapid review

A rapid review uses streamlined systematic-review methods to meet a decision timeline. Possible modifications include narrower eligibility, fewer databases, restricted grey-literature searching or altered screening arrangements. The modifications and their likely consequences must be stated. “Rapid” should describe an explicitly adapted method, not hurried work with undocumented shortcuts.

Umbrella review or overview of reviews

An umbrella review synthesises findings from existing reviews rather than returning directly to all primary studies. It is useful when multiple systematic reviews address related questions, but overlap among reviews, differences in methods and outdated searches require careful management.

Evidence map and related approaches

Evidence maps classify and display the distribution of research across dimensions such as population, intervention, outcome and design. They are particularly useful for showing concentrations and absences of evidence, but they do not automatically establish whether an observed gap should be filled.

Matching review purpose to approach

illustrative

Table 1. Examples of review purposes and possible approaches

Intended product	Possible approach	Central methodological emphasis
Concise proposal background	Focused narrative review	Balanced context and explicit boundaries
Effect of reminders on test completion	Systematic review of intervention effects	Focused eligibility, comprehensive search and risk-of-bias assessment
Range of barriers and study methods	Scoping review	Broad mapping and transparent charting
Women’s experiences of follow-up	Qualitative evidence synthesis	Context, meaning and interpretive synthesis
Decision required within six weeks	Rapid review	Pre-specified methodological streamlining
Summary of several existing reviews	Umbrella review	Review-level appraisal and overlap management

Note: The appropriate choice also depends on whether a current, high-quality review already exists.

Choosing an approach

DECISION GUIDE

Choose the review by answering six questions

1. What decision or knowledge need will the review address?
2. Is the question broad and mapping-oriented or focused and answer-oriented?
3. Which evidence types are required?
4. Is critical appraisal necessary for the intended conclusion?
5. What level of search comprehensiveness and reproducibility is required?
6. What time, expertise, database access and reviewer capacity are available?

The final protocol should describe the actual methods rather than rely only on a review label.

The same topic can support different legitimate reviews. For postpartum follow-up, a scoping review could map barriers and interventions, while a systematic review could estimate the effect of reminder systems. The review purpose determines the question and evidence-selection logic.

Review families rather than a rigid hierarchyMMed extension

Review types are better understood as methodological families than as a single hierarchy from weak to strong. A focused systematic review is not inherently superior to a well-conducted scoping review when the aim is to clarify concepts or map research methods. Quality means that the purpose, question and methods are aligned and transparently reported [1,4,5]. Current JBI guidance likewise treats the review question, evidence type, search, appraisal and synthesis as a connected methodological plan [6].

Worked example

WORKED EXAMPLE

Selecting a review for the postpartum follow-up project

Initial need: The team must justify a local observational study and decide which factors to measure.

Available time: Four weeks before protocol submission.

Decision: Conduct a focused background review rather than claim a new systematic review. Search recent systematic and scoping reviews, major guidelines and key primary studies. Document the databases, dates, concepts and source-selection principles.

Separate evidence-synthesis question: The team discovers that reminder interventions have been evaluated in several trials but that no current synthesis is available. This could become a separate systematic-review project with its own protocol, team and comprehensive search.

Reasoning: The proposal review and the intervention-effect review have different products. Combining them casually would delay the primary study and risk producing an incomplete synthesis.

Appraising a stated review type

APPRAISAL CHECKLIST

Questions to ask when reading or planning a review

• Is the purpose and review question explicit?
• Do the search sources and limits fit the claimed scope?
• Are eligibility and selection procedures transparent?
• Is critical appraisal performed when conclusions depend on study trustworthiness?
• Does the synthesis method fit the evidence and question?
• Are limitations of the review process acknowledged?
• Does the title accurately describe the methods actually used?

Suggested protocol or reporting wording

Common mistakes

Knowledge check

A team wants to map how medication adherence has been defined and measured across chronic-disease studies. Which review approach is most directly aligned?

Answer and reasoning

A scoping review is usually well aligned because the purpose is to map concepts, definitions and research methods across a broad literature. A focused systematic review of effects would be more appropriate if the question instead asked whether a particular intervention improves adherence.

Does a systematic review always include meta-analysis?

Answer and reasoning

No. A systematic review refers to the planned and transparent process of identifying, selecting, appraising and synthesising evidence. Meta-analysis is one possible statistical synthesis method. It may be inappropriate when studies are too clinically or methodologically dissimilar, when outcomes cannot be combined meaningfully or when the evidence is qualitative.

Why is a rapid review not merely a systematic review completed quickly?

Answer and reasoning

A defensible rapid review specifies which conventional methods were modified to meet the timeline and explains the implications. Undocumented shortcuts make it impossible to judge the risk of missing or misclassifying evidence.

A proposal cites ten supportive articles but does not discuss conflicting evidence. What is the main concern?

Answer and reasoning

The review may be selectively constructing a justification rather than providing a balanced account of knowledge. The author should describe the search and selection boundaries, examine relevant contradictory findings and explain differences in population, design or measurement.

Key take-home messages

SUMMARY

Key take-home messages

• Literature reviewing supports problem definition, design, measurement and interpretation.
• A background review and a formal evidence-synthesis study serve different purposes.
• Review types should be chosen by the question and intended product, not by prestige.
• Systematic reviews do not always include meta-analysis, and scoping reviews are not inferior systematic reviews.
• Transparent methods are more informative than the review label alone.

References

1. Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J. 2009;26(2):91–108. https://doi.org/10.1111/j.1471-1842.2009.00848.x
2. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71. https://doi.org/10.1136/bmj.n71
3. Baethge C, Goldbeck-Wood S, Mertens S. SANRA—a scale for the quality assessment of narrative review articles. Res Integr Peer Rev. 2019;4:5. https://doi.org/10.1186/s41073-019-0064-8
4. Munn Z, Peters MDJ, Stern C, Tufanaru C, McArthur A, Aromataris E. Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach. BMC Med Res Methodol. 2018;18:143. https://doi.org/10.1186/s12874-018-0611-x
5. Sutton A, Clowes M, Preston L, Booth A. Meeting the review family: exploring review types and associated information retrieval requirements. Health Info Libr J. 2019;36(3):202–222. https://doi.org/10.1111/hir.12276
6. Aromataris E, Lockwood C, Porritt K, Pilla B, Jordan Z, editors. JBI Manual for Evidence Synthesis. Adelaide: JBI; 2024. https://synthesismanual.jbi.global