Abstract
This short report guides the reader through the types of narrative reviews and describes the narrative review process from conception to completion. This report is an overview on the topic of literature reviews and serves to provide guidance regarding how and when to use a narrative review approach. Authors have many purposes for selecting the narrative review of the literature including introducing an original research manuscript, reviewing a critical topic for a scholarly journal, creating an introductory chapter for a thesis, or completing a classroom assignment. Each purpose may include a specific format and may require different components to be included in the research and writing process. This short report provides examples for each section of the narrative review research and writing process.
INTRODUCTION
Reviews of the literature provide a foundation of knowledge for theses, dissertations, grants proposals, research papers, summary articles, books, policy, and evidence-based statements for health professionals. Due to the growing plethora of scientific publications, critical retrieval and reviews of the literature have become more crucial over the past several decades. The easiest way to begin a discussion of literature reviews is to determine the rationale for using this type of presentation of information and analysis.1
A review of the literature is an assessment of what has already been published or presented; these reviews do not present new data. There are two overarching categories of reviews, narrative reviews of the literature and systematic reviews.2 While systematic reviews are not discussed in this short report, it is important to provide a brief definition. The systematic review follows a highly rigorous and systematic method of collecting, critically evaluating, integrating, and presentation of findings across multiple research studies. Systematic reviews present a broader and more objective level of understanding of the existing information than the traditional and more subjective review of the literature. A systematic review of the literature may be used for formulating guidelines for clinical practice. Systematic reviews will be discussed in greater detail in a subsequent report.
A narrative review of the literature is defined as an analysis of scientific information on a specific topic. The author/reviewer must be able to evaluate the study purpose, appropriateness and quality of the methodology, results, and interpretation of the findings of each of the studies selected to review. Narrative reviews are very common in academic disciplines and are a method of appraising and synthesizing the existing evidence.2 Narrative reviews may also be categorized as synthesis research because the reviewer can summarize and interpret existing knowledge from previous primary studies. The narrative review also allows the researcher to present their own unique perspective on the topic.3
The first suggested use for a narrative review of the literature is as a stand-alone topic which constitutes the entirety of the paper for a scholarly journal manuscript.4 By setting the tone of the topic an author may present the known facts and what still needs to be discovered in a chronological or story-like fashion. A narrative review for a scholarly publication is important if the topic is relevant to the discipline or needs updating based on previous published studies or what is presented in textbooks. The narrative review can bring new perspectives to the reader, highlight new information, identify new methodologies, or present new approaches for older study results.3 Literature reviews may also be part of the introduction in a research manuscript to set the tone or significance of the research study. This type of review presents the context of the research question and again, what is known and unknown at the current timeframe.
Sometimes, students may be given a class assignment to review the literature on a specific topic. In this case the student would still consider the rationale for the literature review, frame a question, and select published articles which explain or update the premise. If the student continues to develop the searching process and creates a scholarly manuscript based on the original search, they must still respond to the research question. These questions may also become the basis for further research studies or a graduate thesis.
The narrative review may also create the background for a study proposal, perhaps to an institutional review board, for a grant, or to some other agency.2 In this case, the review is created to establish the rationale for the research study. This type of literature review presents the known facts to date as well as what is not known about the research questions. This type of background information serves to persuade the agency that the questions or topics are important and require further investigation. The review can also convince the reader that the research is outdated, and new or novel research is warranted.
Another reason for writing a literature review is as a formal chapter in a thesis or dissertation. Here, the author presents concrete facts about the research questions that are known and poses the argument that the dissertation has purpose and meaning for the profession or for continuing the work of others.
Defining the Research Question
After deciding to write a narrative literature review appropriate for a scholarly journal, the next step is to determine a research question. This question should relate the rationale for the review to the question it seeks to answer. Formulating a research question will also help drive the literature search in an organized pattern.2
A question that addresses the population, intervention, comparison, and outcome (PICO) may be used in a narrative review, although it is not always necessary. However, PICO questions can help the researcher choose keywords and terms for a clear search strategy.
An example of a PICO question could come from an original question of interest on the topic, such as burning mouth syndrome (BMS). The author could consider the question of how to treat someone with these symptoms. The PICO question may then become the following: for patients with burning mouth syndrome (P) will tricyclic antidepressant (I) compared to benzodiazepines (C) be more effective in relieving the burning sensation (O).5 Without a specific PICO question, formatting the research question still needs to consider what new information exists or what has changed if there are existing clinical practice guidelines. The research question will still require a narrow focus. Since the general topic of burning mouth syndrome is broad, it may need more further delineation before beginning to search the literature.
Mining the Literature
Establishing a research question then helps the researcher create a search strategy. The actual search process for a narrative review defines which search engines or databases were used such as Medline via PubMed, Cumulative Index in Nursing and Allied Health Literature (CINAHL), Dentistry and Oral Sciences, Scopus, or Medline via Ovid. Knowledge of the medical search terms (MeSH) vocabulary system and Boolean logic are extremely helpful with this process. Search filters including time frames, types of research designs, language, and study populations all become relevant inclusion criteria depending on the research question.6
In the BMS example, the production of key words such as burning mouth syndrome, burning mouth treatment, oral tricyclic antidepressant, or benzodiazepines are MeSH terms used in PubMed. The search may result in either too many or too few articles. Burning mouth may be too broad or not recognized in the MeSH terminology. The researcher will then continue to repeat the search until a suitable number of articles are presented that meet the pre-established inclusion criteria.
Search Results
The results can yield numerous articles which relate to the topic or key terms. However, deciding which articles to include in the narrative review is also subjective. The author may gather a great number of articles, yet they have the freedom to select which articles to include and which ones to exclude in the narrative review. The author must try to persuade the reader that the selected articles have relevance to the research question. Utilizing the highest levels of evidence, such as randomized controlled trials or systematic reviews, will demonstrate to the reader that many published articles were analyzed and either do or do not concur with the research question.
In the example of BMS, the author should review all the articles that addressed the research question. However, if the topic has already been well studied and published in the literature, then the author might consider a slightly different topic or some other modification that has not been published previously.7 The focus of the narrative review may be to present information that is new and novel on the topic or missing from previous published studies. The author will then select articles that relate to the question.
The author should review the abstracts of the articles on the first screening and then follow up by reading the full text version of the selected articles. Each article must be read for its content and applicable conclusion. Authors will need to identify which published articles have meaning to the research question being assessed. Authors must then analyze the study findings and apply them to the research question. It is more than a matter of finding interesting articles and providing summaries of the studies; the review must take a novel approach to the existing literature and the research question.2
Writing the Review
Checklists have long been shown to break complex projects and procedures into manageable tasks. Library guides or checklists are widely available to assist the author in confirming that all aspects of the process have been addressed in the manuscript as required. A checklist will address such topics as the introduction, organization and writing qualities, presentation of studies reviewed, evidence of analysis synthesis and critique, and conclusion.8 Other categories may include topics on the coverage, synthesis, methodology, significance, and rhetoric of the articles.9 Checklist questions will help the author address the various components of each section in a paper under consideration for publication. Author should always refer to the related author guidelines and checklists before beginning to write a narrative review.
The following sections suggested for inclusion and structuring a narrative review from the Journal of Dental Hygiene author information and guidelines.10 The items listed remind the author to check for these points in each section.
Introduction and Objectives
This first section of the narrative review is the introduction. As stated previously, this section guides the reader regarding the rationale for the review. It summarizes the research question and indicates the intent of the review. The author states the premise of the review and the structure to be utilized; unusual terms should also be defined in this section. The author’s direction and premise for the review should be clear to the reader. The objectives of the review may also be stated in the introduction or as a separate section. This section can also suggest research goals and the specific aims of the review.
Methods
The author now presents the methods for the narrative search. The process differs from presenting facts about the methods for a research study. Here the author presents the methods used to actually search for the information and which sources or databases were used in the search. In addition, the search for included articles can be performed by one author, at any level, including junior authors. The search engines used along with the inclusion and exclusion criteria of the search are described here. The author must be clear to define which limits, keywords or terms, or which categories were used in the search.
Results
After an adequate number of articles have been found, the author, as the content expert, begins to analyze the full-text articles. Using a pro and con approach allows the author to narrow the number of articles to be considered for the review. The author should be left with meaningful published articles to analyze and present in the review.
Results are presented subjectively, in a manner determined by the author. Search results might be presented in a table or some format to allow the reader to visualize which articles were included in the review. Graphics can be created to illustrate the review of the articles however they are rarely taken directly from the published articles and always require proper citations. The formatting for the results section is not as strict as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) format for a systematic review. The PRISMA guidelines should not be applied to the narrative review process as the PRISMA format is specifically for systematic reviews.11 However, a table is very useful and could list the articles and the rationale for inclusion, a summary of the conclusions or descriptions of how the articles compare. It can be helpful to review other narrative reviews from scholarly publications to be familiar with the different ways search results can be displayed.
Discussion
The discussion is perhaps the most difficult aspect of writing a narrative review. The author must synthesize and apply the findings of the articles to the research question. Again, this is not a summarization of each article included in the review. The discussion includes commentary about the research methods, overall results, shortcomings, trends, limitations, or applications of the findings. In the case of the BMS example, the author selected articles that presented the advantages and disadvantages of each intervention and assessed the conclusions accordingly. The author could then make the point whether or not there were significant differences in the interventions and suggest which interventions might bring a more desired outcome. The articles can be presented in the discussion by themes, methodology, chronology, or issues according to the research question.2 The author can add subsections depending upon the framework or included articles. The author may also present their own unique perspective or opinion on the topic provided that the guidelines are followed for the specific scholarly publication. The manner in which the literature review findings are presented may also be determined by the author guidelines of the journal and may vary based on the publication.
Conclusion
The author returns to the research question, the rationale for study design, the purpose of the studies investigated and any implications of the findings in the conclusion paragraph. The conclusion of the narrative review provides a summary of the findings and guides the reader to further research or to draw new conclusions. The conclusion should not present new information or continue to discuss the research question.
Abstract
The abstract is the last item in the writing process.6 Writing the abstract allows the author(s) the opportunity to reflect upon the research question and results. Abstracts can be structured listing the purpose, methods, results and conclusion or a non-structured summary of the narrative review depending on the author guidelines of the journal.6 Abstracts are written in the third person and do not include any reference citations. Abstracts should be a succinct summary of the full-text narrative review. Article titles and keywords should be chosen to aid readers to be able to duplicate the search or consider its applications.
SUMMARY
In summary, this short report attempts to guide the author in creating a scholarly narrative review of the literature. Narrative reviews may be submitted as a manuscript for publication, included in an introduction for a research proposal or expanded into a thesis chapter. In the rapidly changing world of scientific research and information dissemination, narrative reviews of the literature create a significant impact by keeping oral health care professionals up to date and facilitating the evidence-based decision-making process.
Footnotes
NDHRA priority area, Professional development: Education (evaluation).
DISCLOSURE
The authors have no conflicts of interest to disclose.
- Received September 26, 2023.
- Accepted January 17, 2024.
- Copyright © 2024 The American Dental Hygienists’ Association
