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Traditional reviews vs. systematic reviews

Posted on 3rd February 2016 by

Tutorials and Fundamentals

Millions of articles are published yearly(1), making it difficult for clinicians to keep abreast of the literature. Reviews of literature are necessary in order to provide clinicians with accurate, up to date information to ensure appropriate management of their patients. Reviews usually involve summaries and synthesis of primary research findings on a particular topic of interest and can be grouped into 2 main categories; the ‘traditional’ review and the ‘systematic’ review with major differences between them.

Traditional reviews provide a broad overview of a research topic with no clear methodological approach(2). Information is collected and interpreted unsystematically with subjective summaries of findings. Authors aim to describe and discuss the literature from a contextual or theoretical point of view. Although the reviews may be conducted by topic experts, due to preconceived ideas or conclusions, they could be subject to bias.

Systematic reviews are overviews of the literature undertaken by identifying, critically appraising and synthesising results of primary research studies using an explicit, methodological approach(3). They aim to summarise the best available evidence on a particular research topic.

The main differences between traditional reviews and systematic reviews are summarised below in terms of the following characteristics: Authors, Study protocol, Research question, Search strategy, Sources of literature, Selection criteria, Critical appraisal, Synthesis, Conclusions, Reproducibility, and Update.

Traditional reviews

  1. Authors: One or more authors usually experts in the topic of interest
  2. Study protocol: No study protocol
  3. Research question: Broad to specific question, hypothesis not stated
  4. Search strategy: No detailed search strategy, search is probably conducted using keywords
  5. Sources of literature: Not usually stated and non-exhaustive, usually well-known articles. Prone to publication bias
  6. Selection criteria: No specific selection criteria, usually subjective. Prone to selection bias
  7. Critical appraisal: Variable evaluation of study quality or method
  8. Synthesis: Often qualitative synthesis of evidence
  9. Conclusions: Sometimes evidence based but can be influenced by author’s personal belief
  10. Reproducibility: Findings cannot be reproduced independently as conclusions may be subjective
  11. Update: Cannot be continuously updated

Systematic reviews

  1. Authors: Two or more authors are involved in good quality systematic reviews, may comprise experts in the different stages of the review
  2. Study protocol: Written study protocol which includes details of the methods to be used
  3. Research question: Specific question which may have all or some of PICO components (Population, Intervention, Comparator, and Outcome). Hypothesis is stated
  4. Search strategy: Detailed and comprehensive search strategy is developed
  5. Sources of literature: List of databases, websites and other sources of included studies are listed. Both published and unpublished literature are considered
  6. Selection criteria: Specific inclusion and exclusion criteria
  7. Critical appraisal: Rigorous appraisal of study quality
  8. Synthesis: Narrative, quantitative or qualitative synthesis
  9. Conclusions: Conclusions drawn are evidence based
  10. Reproducibility: Accurate documentation of method means results can be reproduced
  11. Update: Systematic reviews can be periodically updated to include new evidence

Decisions and health policies about patient care should be evidence based in order to provide the best treatment for patients. Systematic reviews provide a means of systematically identifying and synthesising the evidence, making it easier for policy makers and practitioners to assess such relevant information and hopefully improve patient outcomes.


  1. Fletcher RH, Fletcher SW. Evidence-Based Approach to the Medical Literature. Journal of General Internal Medicine. 1997; 12(Suppl 2):S5-S14. doi:10.1046/j.1525-1497.12.s2.1.x. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1497222/
  2. Rother ET. Systematic literature review X narrative review. Acta paul. enferm. [Internet]. 2007 June [cited 2015 Dec 25]; 20(2): v-vi. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-21002007000200001&lng=en. http://dx.doi.org/10.1590/S0103-21002007000200001
  3. Khan KS, Ter Riet G, Glanville J, Sowden AJ, Kleijnen J. Undertaking systematic reviews of research on effectiveness: CRD’s guidance for carrying out or commissioning reviews. NHS Centre for Reviews and Dissemination; 2001.


Weyinmi Demeyin

Hi, I have a dental background and am currently a PhD student at the University of Exeter. I have an interest in evidence based research, and its application to meet an individual’s specific need. The focus of my research is N of 1 Trials and the individualisation of drug treatments. View more posts from Weyinmi

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    7th March 2024 at 9:19 pm
    Reply to ALFRED
  • Rosemary Chigevenga

    Thank you very much for the information here.
    My question is : Is it possible for me to do a systematic review which is not directed toward patients but just a specific population? To be specific can I do a systematic review on the mental health needs of students?

    6th February 2024 at 5:08 pm
    Reply to Rosemary
    • Emma Carter

      Hi Rosemary, I wonder whether it would be useful for you to look at Module 1 of the Cochrane Interactive Learning modules. This is a free module, open to everyone (you will just need to register for a Cochrane account if you don’t already have one). This guides you through conducting a systematic review, with a section specifically around defining your research question, which I feel will help you in understanding your question further. Head to this link for more details: https://training.cochrane.org/interactivelearning

      I wonder if you have had a search on the Cochrane Library as yet, to see what Cochrane systematic reviews already exist? There is one review, titled “Psychological interventions to foster resilience in healthcare students” which may be of interest: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD013684/full You can run searches on the library by the population and intervention you are interested in.

      I hope these help you start in your investigations. Best wishes. Emma.

      9th February 2024 at 9:24 am
      Reply to Emma
  • Alex

    La revisión sistemática vale si hay solo un autor?

    7th September 2022 at 1:01 am
    Reply to Alex
    • Emma Carter

      HI Alex, so sorry for the delay in replying to you. Yes, that is a very good point. I have copied a paragraph from the Cochrane Handbook, here, which does say that for a Cochrane Review, you should have more than one author.

      “Cochrane Reviews should be undertaken by more than one person. In putting together a team, authors should consider the need for clinical and methodological expertise for the review, as well as the perspectives of stakeholders. Cochrane author teams are encouraged to seek and incorporate the views of users, including consumers, clinicians and those from varying regions and settings to develop protocols and reviews. Author teams for reviews relevant to particular settings (e.g. neglected tropical diseases) should involve contributors experienced in those settings”.

      Thank you for the discussion point, much appreciated.

      21st September 2022 at 10:52 am
      Reply to Emma
  • Nicolas Nicolas

    I’d like to ask you a question: what’s the difference between systematic review and systematized review? In addition, if the screening process of the review was made by only one author, is still a systematic or is a systematized review?

    23rd February 2022 at 2:19 pm
    Reply to Nicolas
    • Emma Carter

      Hi. This article from Grant & Booth is a really good one to look at explaining different types of reviews: https://onlinelibrary.wiley.com/doi/10.1111/j.1471-1842.2009.00848.x It includes Systematic Reviews and Systematized Reviews. In answer to your second question, have a look at this Chapter from the Cochrane handbook. It covers the question about ‘Who should do a systematic review’. https://training.cochrane.org/handbook/current/chapter-01

      A really relevant part of this chapter is this: “Systematic reviews should be undertaken by a team. Indeed, Cochrane will not publish a review that is proposed to be undertaken by a single person. Working as a team not only spreads the effort, but ensures that tasks such as the selection of studies for eligibility, data extraction and rating the certainty of the evidence will be performed by at least two people independently, minimizing the likelihood of errors.”

      I hope this helps with the question. Best wishes. Emma.

      24th February 2022 at 11:10 am
      Reply to Emma

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