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On-line version ISSN 1982-0194
Acta paul. enferm. vol.20 no.2 São Paulo Apr./June 2007
Systematic literature review X narrative review
Scientific literature review articles are methodological studies which use database searches to retrieve results of research, and have as their mail goal the objective and theoretical discussion of a specific topic or theme.
Two main types of review articles are commonly found in the scientific literature: Systematic and narrative review of the literature. These two types of review articles have distinct characteristics and goals.
Narrative literature review articles are publications that describe and discuss the state of the science of a specific topic or theme from a theoretical and contextual point of view. These types of review articles do not list the types of databases and methodological approaches used to conduct the review nor the evaluation criteria for inclusion of retrieved articles during databases search(1). Narrative review consists of critical analysis of the literature published in books and electronic or paper-based journal articles.
Narrative literature review articles have an important role in continuing education because they provide readers with up-to-date knowledge about a specific topic or theme. However, this type of review does not describe the methodological approach that would permit reproduction of data nor answer to specific quantitative research questions. These review articles normally use a qualitative approach using the following headings: Introduction, Development (using necessary sub-headings to divide and discuss appropriately the topic), Discussion, and References.
On the other hand, systemic literature review "is a well planned review to answer specific research questions using a systematic and explicit methodology to identify, select, and critically evaluate results of the studies included in the literature review"(2). Systematic literature review articles are considered original work because they are conducted using rigorous methodological approaches.
Methodological approaches to conduct a systematic literature review can be found in Cochrane Handbook of Systematic Reviews of Interventions(3) published by the Cochrane Collaboration as well as in the CRD's Guidance for Carrying Out or Commissioning Reviews published by the NHS Centre for Reviews and Dissemination(4).
In Brazil, researchers often use the seven steps recommended by Cochrane Collaboration (3) to conduct a systematic literature review. These seven steps are:
a) Posing a Research Question - A systematic literature review must start with a well formulated research question that contains well defined types of patients/illness and interventions that help in the decision-making process determining which articles to include in the literature review.
b) Locating Studies Use several sources to locate and retrieve scientific studies. These sources should include main databases such as Medline, Cinahl, Embase, Lilacs, Cochrane Controlled Trials Database, SciSearch and other information sources such as articles published in conference proceedings, specialized studies, and manual search of articles published in journals that are not indexed in the major scientific databases. A detailed description of the approach should be described for each one of these types of sources used.
c) Critical Evaluation of the Studies Use specific criteria to determine the validity of the selected studies. This approach facilitates the decision-making process determining which articles would be included in the literature review. Studies that are not included in the literature review must be cited and have a rationale for exclusion.
d) Data Collection Describe each study's methodological approach (variables, sample, measures, and data analysis) and findings, which allow comparison between and/or among the selected studies.
e) Data Analysis and Reporting Studies should be grouped together according to their methodological similarities. This approach must be addressed in the project. Numerical and graphical presentation of the results should also be addressed in the project to facilitate reader understanding of the findings. Statistical analysis and synthesis of the results consists of meta-analysis, a statistical method to integrate the results of systematic reviews.
f) Interpretation of the Findings this is determined by the strength of evidence, utilization of the findings, costs and current practice, which dictates the balance between benefits and risks.
g) Refinement and Updating the Review when published, a systematic review will be scrutinized by the scientific community who will then make recommendations that must be addressed in subsequent reviews, updating the review topic when new studies about the topic are published.
The NHS/York recommends another approach to conduct a systematic literature review(4), This approach consists of three stages using nine-step, which is not significantly different from the steps of the Cochrane Collaboration(3).
Thus, systematic literature review uses rigorous methodology to prevent shortcuts and bias in conducting a review. Meta-analysis is a statistical method to integrate the results of the selected studies included in a systematic literature review.
Table 1 summarize the main difference between systematic literature review and narrative literature review
1. Bernardo WM, Nobre MRC, Jatene FB. A prática clinica baseada em evidências. Parte II: buscando as evidências em fontes de informação. Rev Assoc Med Bras. 2004; 50(1):1-9.
2. Castro AA. Revisão sistemática e meta-aálise [texto na Internet] [citado 2006 Mai 21]. Disponível em: http://www.metodologia.org/ meta1.PDF
3. Clarke M, Oxman AD, editors. Cochrane Reviewers' Handbook 4.1 [updated June 2000]. In: Review Manager (RevMan) [Computer program]. Version 4.1. Oxford, England: The Cochrane Collaboration, 2000. Available from: http://www.cochrane.dk/ cochrane/handbook/hanbook.htm
4. Khan KS, Ter Riet G, Glanville J, Sowden AJ, Kleijnen J, editors for the NHS Centre for Reviews and Dissemination (CRD). Undertaking Systematic Reviews of Research on Effectiveness. CRD's Guidance for Carrying Out or Commissioning Reviews. 2nd ed. New York: NHS Centre for Reviews and Dissemination, University of York, 2000.[ CRD Report No. 4]. Available from: http://www.york.ac.uk/ inst/cdr/report4.htm
Edna Terezinha Rother
Editora Técnica da Acta Paulista de Enfermagem