Table 1: Literature reviews vs systematic reviews. Literature review. Methodological stage. Systematic review. Introduces context and current thinking, often.
Editorials
doi: 10.1111/1753-6405.12393
Literature reviews vs systematic reviews Priscilla Robinson and John Lowe ANZJPH Editors
References
A
common type of submission at any Journal is a review of the published information related to a topic. These are often returned to their authors without review, usually because they are literature reviews rather than systematic reviews. There is a big difference between the two (Table 1). Here, we summarise the differences, how they are used in academic work, and why a general literature review is not suitable for publication in a contemporary journal. Systematic review authors need to both identify the tool they have used for data extraction and the reasons for selecting (or adapting) it. Not all public health problems can be studied using blinded clinical trials, so most evidence for public health interventions is likely to be found in other kinds of studies or, on occasions, in qualitative studies. Most tools have been developed to extract trials data, but there are tools specifically designed for other settings, including public health.1-3 While the strength of evidence provided by the study design is important, just as critical is the rigour with which the study was executed.4 A systematic review sometimes produces results which, inconveniently, contradict common beliefs. For example, in a review of meta-analyses (more than 370,000 individuals) to seek associations between saturated fat intake and cardiovascular events,6 Foster and Wilson showed that although there was a non-significant risk reduction of about 10% when saturated fats were replaced with polyunsaturated fats, there was no significant association between CVD and saturated fat intake.
in all-cause mortality (although not until three years after measurement),7 but shows no particular improvements for any one disease. Another – not insignificant – problem with Vitamin D is in the quality and reliability of the testing: a one-off test is not a reliable indicator of deficiency.8 It is critical that the review question being asked is precise, with inclusion and exclusion criteria. Data extraction techniques are important, as these parameters can change the conclusion drawn by the review authors. For example, Day and Francisco attempted to identify good interventions for social and emotional wellbeing of Indigenous Australians, but despite a comprehensive search strategy and identification of more than 8,000 possibly useful papers, could not come to any conclusions.9 Their main discussion is not about best practice at all, but about the need for agreed outcome definitions among people delivering relevant programs. Some excellent examples of the use of systematic reviews to improve public health are to be found in this journal. Byles’s review of an heterogeneous set of clinical trials of the outcomes of health assessments10 showed that in general these were instrumental in improving the health of older people. Lesley Day and colleagues’ imaginative use of a systematic review linked to government falls-prevention programs11 showed how
1. The Cochrane Public Health Group. The Cochrane Collaboration [Internet]. Melbourne (AUST) [updated 2014 Nov 11; cited 2015 Mar 1]. Available from: http:// ph.cochrane.org/. 2. Rychetnik L, Frommer M. A Schema for Evaluating Evidence on Public Health Interventions [Internet]. Version 4. Melbourne (AUST): National Public Health Partnership, 2001 [cited 2015 Mar 1]. Available from: http://www.health.nsw.gov.au/research/Documents/ schema-for-evaluating-evidence.pdf 3. McCall J, Connor J. Systematic reviews in public health research. Aust N Z J Public Health. 2010:34(4):343–4. 4. Robinson P, Daly J. Producing the evidence we need and validating the evidence we have. J Appl Arts Health. 2014:5(2):245-53. 5. Taylor LE, Swerdfeger AL, Eslick GD. Vaccines are not associated with autism: An evidence-based metaanalysis of case-control and cohort studies. Vaccine. 2014;32(29):3623-9. 6. Foster RH, Wilson N. Review of the evidence for the potential impact and feasibility of substituting saturated fat in the New Zealand diet. Aust N Z J Public Health. 2013;37(4):329–36. 7. Zheng Y, Zhu J, Zhou M, Cui L, Yao W, Liu Y. Meta-analysis of long-term vitamin D supplementation on overall mortality. PLoS One. 2013;8(12):e82109. 8. Lucas R, Neale R. What is the optimal level of vitamin D? Separating the evidence from the rhetoric. Aust Fam Physician. 2014:43(3):119-22. 9. Day A, Francisco A. Social and emotional wellbeing in Indigenous Australians: Identifying promising interventions. Aust N Z J Public Health. 2013:37(4):350–5. 10. Byles JE. A thorough going over: Evidence for health assessments for older persons. Aust N Z J Public Health. 2000:24(2):117–23. 11. Day L, Donaldson A, Thompson C, Thomas M. Integrating proven falls prevention interventions into government programs. Aust N Z J Public Health. 2014:38 (2):122–7. 12. Ward K, Chow MYK, King C, Leask J. Strategies to improve vaccination uptake in Australia, a systematic review of types and effectiveness. Aust N Z J Public Health. 2012:36(4):369–77.
Table 1: Literature reviews vs systematic reviews.
There is the well-known example in the measles-immunisation-and-autism ‘debate’ of a small, single study of doubtful quality influencing public policy. The careful studies conducted since the 1960s (predating any scaremongering), which made a recent metaanalysis of more than 1.25 million children possible, refutes these findings and shows that measles immunisation possibly protects children from autism.5 Vitamin D deficiency seems now to be linked with all manner of diseases from osteoporosis and cancer to infectious diseases and metabolic and autoimmune disorders. The results of one meta-analysis suggest higher vitamin D levels are linked to improvements
2015 vol. 39 no. 2
this approach can be used to inform and enhance government policy. Kirsten Ward and colleagues undertook an interesting review to identify strategies for improving vaccine uptake in Australia.12
Literature review
Methodological stage
Systematic review
Introduces context and current thinking, often without a specific question, is general and covers several aspects of a topic.
Focus of review
Uses a precise question to produce evidence to underpin a piece of research. A stand-alone piece of research, it should be conducted prior to undertaking further research, particularly in higher degree theses.
Finds papers through a fairly random process, usually searching only a few databases. Use of grey literature common, but not usually systematic.
Methods for data collection
Searches of several specified databases using precise search terms; a similar systematic search of grey literature sometimes included, depending on the question.
Papers are read, ‘take home’ messages used in the review.
Methods for data extraction
Data extraction tool used to identify precise pieces of information; two or more researchers undertake data extraction.
Anything up to 150 papers or more.
Number of papers included in review
Usually less than 50 papers; often fewer than 10.
Writer interprets the meaning of the results.
Methods for data analysis
Recognised, referenced, methods for data analysis; includes analysis of methods, rigour of conduct of research, strength of evidence, and so on.
Prose paper, occasionally supported with diagrams.
Methods for data presentation
PRISMA/CONSORT or similar chart/table of included papers.
Not suitable for Journal publication.
Publication
Might be suitable for Journal publication.
Actions/directions informed by evidence of various kinds drawn from included papers.
Outcome
Actions/directions are based on evidence from reviewed papers.
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