Comprehensive, Narrative, and Systematic Literature Review: Approaches for Synthesising Evidence

A literature review is a critical and systematic examination of scholarly sources (such as books, research articles, dissertations, conference papers, and other relevant publications) on a specific topic or research question. It is a comprehensive summary and evaluation of existing knowledge, theories, and findings related to a particular subject area.

The purpose of a literature review varies depending on the context and objectives of the study. It can be conducted as a standalone work, such as a review paper, or as a preliminary step in a research project to establish a theoretical framework and identify research gaps. Regardless of its specific purpose, a literature review involves the following key elements:

1. Identification and selection of sources

2. Evaluation and analysis of sources

3. Synthesis and organisation of information

4. Identification of research gaps

5. Analysis and interpretation of findings

6. Conclusion and recommendations

Overall, a literature review serves as a foundation for research by establishing a context for the study, informing theoretical frameworks, and providing a comprehensive overview of existing knowledge. It aids researchers in understanding the current state of research, identifying areas for further investigation, and positioning their work within the broader academic discourse.

A. Comprehensive Literature Review

Writing a comprehensive literature review is a fundamental aspect of academic research. It establishes a foundation for new inquiries by synthesising existing knowledge. A well-executed literature review identifies gaps in current research and provides context and justification for future studies. Researchers should adopt a systematic approach that defines the scope, organises the literature, and critically evaluates sources.

The initial step is to clearly define the scope of the review by formulating specific research questions or objectives. This focus ensures that the review remains relevant and manageable. Booth, Sutton, and Papaioannou (2016) emphasise the need to establish explicit inclusion and exclusion criteria to maintain clarity and direction throughout the review process. For instance, limiting the search to peer-reviewed articles published within the last decade can help capture the most current and pertinent information.

Organising the literature effectively is crucial for identifying patterns, themes, and areas of consensus or debate. Hart (2018) suggests categorising studies based on themes, methodologies, or theoretical frameworks to construct a coherent narrative. Utilising tools such as concept mapping or citation management software can aid in systematically arranging the literature, facilitating a more comprehensive analysis.

Critical evaluation of the selected sources is essential to assess their quality, relevance, and contribution to the field. Hart (2018) advises researchers to critically analyse research design, sample size, and potential biases. This rigorous appraisal ensures that the literature review is built upon robust and credible studies, enhancing the overall integrity of the research.

B. Narrative Literature Review

Writing a narrative literature review involves synthesising and critically analysing existing research on a particular topic. Unlike systematic reviews, narrative reviews provide a broader perspective, often focusing on themes, trends, and gaps in the literature. To create an effective narrative literature review, writers should follow several key strategies.

The first step in writing a narrative literature review is clearly defining its scope and purpose. According to Green et al. (2006), specifying the review's objective helps to narrow the selection of studies and ensures the review remains focused. Without a clear research question or objective, the review can become too broad, making it difficult to provide meaningful insights. For example, a review of educational interventions might focus on specific age groups, teaching strategies, or geographic regions. This clarity allows the writer to align their review with the needs of their target audience and contribute effectively to the academic discourse.

Another critical aspect is organising the review thematically or conceptually. A thematic structure groups studies by recurring themes or concepts, allowing the writer to synthesise findings across studies. Baumeister and Leary (1997) emphasise that such an organisation facilitates meaningful comparisons and highlights patterns in the literature. For instance, a review on mental health interventions might organise studies into themes such as "cognitive-behavioural therapy," "pharmacological treatments," and "community-based approaches." This approach helps readers understand the broader trends and connections within the field.

Critical literature evaluation is essential to identify gaps, inconsistencies, and future research opportunities. Writers should assess the strengths and limitations of the studies they include, providing a balanced perspective. Baumeister and Leary (1997) argue that highlighting methodological flaws, sampling biases, or areas of insufficient evidence strengthens the review's credibility. Moreover, critical evaluation ensures that the review advances knowledge in the field by identifying areas that warrant further investigation.

Finally, the review should comprehensively synthesise the findings, offering clear conclusions and actionable recommendations. Summarising key points from the literature allows writers to identify overarching trends and implications. Green et al. (2006) suggest that a well-crafted conclusion ties the findings back to the review's objective, provides insights into the topic, and suggests avenues for future research.

C. Systematic Literature Review (SLR)

In research and academia, staying up-to-date with the ever-expanding body of knowledge is paramount. However, the sheer volume of scholarly publications can be overwhelming, making it difficult to extract meaningful insights. This is where systematic literature review (SLR) comes into play. A systematic literature review is a rigorous and comprehensive approach to synthesising existing research in a particular field or topic.

A systematic literature review is a systematic and transparent method for identifying, evaluating, and synthesising relevant research studies on a specific research question or topic. Unlike traditional literature reviews, which may be prone to bias and subjectivity, SLRs follow a well-defined and replicable methodology. By employing explicit search strategies and predefined inclusion and exclusion criteria, SLRs aim to minimise bias and ensure a comprehensive, unbiased review of the available evidence, as depicted in The Logic of Science's Hierarchy of Scientific Evidence.

An SLR is a rigorous and structured approach to synthesising existing research in a specific field or topic. By following a well-defined methodology, SLRs provide researchers with a comprehensive overview of the available evidence, helping to inform decision-making, identify research gaps, and advance knowledge. They are also invaluable resources for researchers, policymakers, and practitioners.

a. Types of SLR

There are various types of SLR, each designed with specific focuses and objectives. Below are some of the most commonly recognised types, along with their unique characteristics:

1. Traditional/Systematic review

   1. This is the most basic type of systematic literature review.

   2. It aims to provide a comprehensive and unbiased summary of the evidence on a specific research question or topic.

   3. It follows a systematic methodology for searching, selecting, and evaluating studies.

2. Meta-analysis

   1. A meta-analysis is a quantitative, systematic review that involves statistical analysis of data from multiple studies.

   2. It aims to synthesise and combine the results of individual studies to generate an overall effect size or estimate.

   3. Meta-analysis is particularly useful when studies have similar designs, outcomes, and measures.

   4. A systematic analysis often precedes a meta-analysis.

      1. The systematic analysis identifies studies, while the meta-analysis combines their quantitative data.

      2. Not all systematic reviews include meta-analyses, but all meta-analyses are based on systematic reviews.

3. Meta-synthesis

   1. Meta-synthesis is a qualitative systematic review method that synthesises findings from qualitative studies.

   2. It involves analysing and interpreting findings, themes, and concepts across multiple studies to better understand a particular phenomenon or research question.

4. Scoping review

   1. A scoping review aims to map the existing literature on a broad research topic.

   2. It provides an overview of the quantity, nature, and distribution of research in a particular field, highlighting key concepts, gaps, and emerging trends.

   3. Scoping reviews often do not assess study quality or conduct detailed data synthesis.

5. Systematic mapping review

   1. A systematic mapping review is similar to a scoping review but focuses on systematically mapping the existing literature based on predefined criteria.

   2. It aims to identify the extent, nature, and distribution of research in a particular area, including types of studies, methodologies, and geographic coverage.

6. Mixed methods review

   1. A mixed-methods review combines quantitative and qualitative studies.

   2. It involves synthesising data from various study designs, methodologies, and data types to gain a comprehensive understanding of a research question or topic.

7. Realist review

   1. Realist reviews explore how and why interventions work (or do not) in specific contexts.

   2. They focus on developing program theory models by synthesising evidence from multiple sources, including empirical studies, theoretical frameworks, and stakeholder perspectives.

Above are some of the main types of systematic literature reviews. It is important to note that the specific approach and terminology may vary across disciplines and research fields. The choice of review type depends on the research question, available evidence, and the goals of the review. Below are the steps for conducting an SLR.

D. Comprehensive vs. Narrative vs. Systematic Literature Reviews

A comprehensive literature review aims to provide an extensive overview of all available literature related to a specific topic. It is often broad in scope and may incorporate studies from various disciplines to offer a well-rounded perspective. According to Torraco (2016), this approach is useful when synthesising diverse knowledge or identifying research gaps across multiple fields. Comprehensive reviews are typically less constrained by methodological rigour, which can result in a more flexible but less reproducible synthesis. Here are two examples of research on the implementation of a narrative literature review approach. Here is an example of research on implementing a comprehensive literature review approach.

In contrast, a narrative literature review is more selective and interpretative. It summarises and critiques existing literature to provide context for a research question or argument (Baumeister & Leary, 1997). Narrative reviews often emphasise the author's perspective, allowing for a more subjective analysis. This approach is particularly beneficial in theoretical discussions or when exploring emerging areas of study. However, Grant and Booth (2009) caution that narrative reviews may be prone to bias, as they rely on the author’s judgment in selecting and interpreting sources. Here is an example of research on the implementation of a narrative literature review approach.

A systematic literature review, on the other hand, is the most rigorous and structured of the three approaches. It involves a transparent and replicable process for systematically identifying, evaluating, and synthesising relevant studies. This method typically follows predefined protocols and includes a comprehensive search strategy, strict inclusion and exclusion criteria, and an assessment of the quality of included studies (Higgins et al., 2022). Systematic reviews are the most reliable method for gathering evidence in healthcare and social sciences, reducing bias and supporting decision-making (Liberati et al., 2009). Here is an example of research on the implementation of a systematic literature review approach.

E. Steps to Conduct an SLR Solutions

1. Question

   1. The first step in conducting an SLR is formulating a clear, focused research question.

   2. This question should guide the entire review process and provide a framework for selecting relevant studies.

   3. It is crucial to ensure the research question is specific, relevant, and answerable through the available literature.

2. Search

   1. A systematic and comprehensive search strategy is crucial for identifying relevant studies.

      1. It is essential to document the search strategy to ensure transparency and replicability.

   2. This involves identifying relevant keywords, synonyms, and controlled vocabulary terms associated with the research question.

   3. This involves searching multiple electronic databases, including academic journals, conference proceedings, and grey literature.

      1. Grey literature refers to materials and research produced by organisations outside traditional commercial or academic publishing and distribution channels, including government reports, conference proceedings, graduate dissertations, and unpublished clinical trials.

   4. Electronic databases, such as PubMed, Scopus, or Web of Science, are commonly used to conduct literature searches.

3. Screen and select

   1. After applying the search strategies, the retrieved studies must be screened against predefined inclusion and exclusion criteria.

      1. The inclusion criteria should align with the research question and study objectives, while the exclusion criteria help filter out irrelevant or low-quality studies.

   2. Initially, titles and abstracts are screened to identify potentially relevant studies.

   3. Then, a full-text assessment is conducted for the selected studies.

4. Extract

   1. Once the studies are selected, relevant data needs to be extracted systematically.

   2. A standardised data extraction form should be developed to collect essential information from each study, including study design, sample size, methodology, key findings, and other relevant details.

   3. This step ensures consistency and facilitates data analysis and synthesis in later stages.

5. Assess

   1. A quality assessment ensures the reliability and validity of the included studies.

   2. This step involves evaluating each study's methodological rigour, potential biases, and overall quality.

   3. Various tools and frameworks, such as the Cochrane Risk of Bias Tool or the Joanna Briggs Institute Critical Appraisal Checklist, can assist in assessing study quality.

6. Synthesise and analyse

   1. The extracted data from the selected studies are synthesised and analysed to identify patterns, themes, and relationships.

   2. Quantitative meta-analysis and thematic analysis can be employed depending on the nature of the research question and the available data.

   3. Quantitative analysis uses statistical techniques to synthesise data from multiple studies, while qualitative analysis identifies common themes and draws meaningful conclusions.

7. Interpret and report

   1. The final step of an SLR is to interpret and report the results clearly and transparently.

   2. The findings should be summarised and address the research question and objectives.

   3. Any limitations or biases should be acknowledged, and implications for future research and practice should be discussed.

   4. Adhering to reporting guidelines, such as PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses), is crucial to enhancing the transparency and reproducibility of the review.

F. Writing an SLR Using PRISMA  Solutions

Writing a systematic literature review (SLR) is a structured process that requires clear guidelines to ensure transparency and reproducibility. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) provides a robust framework for researchers conducting and reporting SLRs. PRISMA focuses on enhancing the clarity and comprehensiveness of reviews, helping researchers avoid bias and ensure methodological rigour (Page et al., 2021). Key steps include defining a research question, identifying relevant studies, assessing their quality, and systematically synthesising findings.

The first step in a PRISMA-guided SLR is to define a clear research question using frameworks such as PICO (Population, Intervention, Comparison, Outcome) to ensure the question is specific and actionable (Liberati et al., 2009). This step is crucial because it determines the scope of the review and the inclusion criteria for studies. Researchers must also develop a comprehensive search strategy that uses multiple databases and combines keywords with Boolean operators to capture all relevant literature. The PRISMA flow diagram is essential for tracking the selection process and documenting the number of records identified, screened, excluded, and included in the final review (Page et al., 2021).

Critical appraisal of the selected studies is another essential step. Using validated tools such as the Cochrane Risk of Bias Tool or the Joanna Briggs Institute's critical appraisal tools ensures that included studies meet quality standards (Munn et al., 2018). Researchers should report the results transparently, summarising study characteristics and findings in tables or narrative formats. Finally, the discussion should highlight the implications of the findings, address limitations, and suggest future research directions. By following PRISMA guidelines, researchers can produce high-quality SLRs contributing to evidence-based decision-making.

G. To Sum Up...

In summary, while comprehensive and narrative reviews are more flexible and subjective, systematic reviews offer a structured and reproducible approach. Each method has unique strengths and limitations, making it critical for researchers to align their review type with their specific objectives and the nature of their research questions. Systematic literature reviews offer a robust and structured approach to synthesising existing evidence, identifying research gaps, and informing decision-making. Their benefits extend beyond individual studies, advancing knowledge, evidence-based practice, and policy development.

When approaching a literature review, it is essential to understand the differences between comprehensive, narrative, and systematic approaches. Each serves a distinct purpose and requires varying levels of rigour and structure. Researchers need to thoughtfully choose the most suitable research method, taking into account their specific objectives and the broader context of their inquiry. This careful selection process is crucial as the chosen method will significantly influence the validity and reliability of their findings.

Despite these limitations, systematic literature reviews remain valuable for summarising existing evidence, identifying research gaps, and informing decision-making. Recognising and addressing these potential disadvantages can help researchers mitigate their impact and enhance the quality and reliability of the review findings. By following the step-by-step guide outlined in this article, researchers can effectively apply the SLR methodology, ensuring rigour, transparency, and reliability throughout the review process.

References

• Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews. Review of General Psychology, 1(3), 311–320. https://doi.org/10.1037/1089-2680.1.3.311

• Booth, A., Sutton, A., & Papaioannou, D. (2016). Systematic approaches to a successful literature review (2nd ed.). SAGE Publications.

• Grant, M. J., & Booth, A. (2009). A typology of reviews: An analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26(2), 91–108. https://doi.org/10.1111/j.1471-1842.2009.00848.x

• Green, B. N., Johnson, C. D., & Adams, A. (2006). Writing narrative literature reviews for peer-reviewed journals: Secrets of the trade. Journal of Chiropractic Medicine, 5(3), 101–117. https://doi.org/10.1016/S0899-3467(07)60142-6

• Hart, C. (2018). Doing a literature review: Releasing the research imagination (2nd ed.). SAGE Publications.

• Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., & Welch, V. A. (Eds.). (2022). Cochrane handbook for systematic reviews of interventions (version 6.3). Cochrane. https://training.cochrane.org/handbook

• Liberati, A., Altman, D. G., Tetzlaff, J., Mulrow, C., Gøtzsche, P. C., Ioannidis, J. P. A., Clarke, M., Devereaux, P. J., Kleijnen, J., & Moher, D. (2009). The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: Explanation and elaboration. PLoS Medicine, 6(7), e1000100. https://doi.org/10.1371/journal.pmed.1000100

• Torraco, R. J. (2016). Writing integrative literature reviews: Using the past and present to explore the future. Human Resource Development Review, 15(4), 404–428. https://doi.org/10.1177/1534484316671606

Let's Recall...

1. What are the main differences between comprehensive, narrative, and systematic literature reviews?

2. How does evaluating sources strengthen a literature review?

3. Why is it important to find gaps in research during a literature review?

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