Literature Searching and Reviews

Systematic reviews, or systematic overview articles, aim to answer a precisely defined research question by collecting all evidence that fits into specifically defined criteria. To ensure quality and minimize bias, a systematic review is conducted using prior systematic, transparent and unambiguous methods (1, 2).
These methods will be applicable for both qualitative and quantitative studies.

A systematic review consists of a number of (possible) steps. Depending on the topic of the review, a quantitative analysis (meta-analysis) will be included.
The overview below outlines the common steps involved in preparing the review (there may be more or fewer steps in the process) (3):

• Purpose and Scope
  Including clarification of topic and existing reviews. 
   
• Creating Research Question and protocol
  There are models (conceptualization models) that can be used to formulate research questions, as well as guides that can assist in creating a protocol.. (Covidence. (2024). A practical guide: Protocol Development for Systematic Reviews. Veritas Health Innovation/ you can download this guide (research questions based on PICO))
• Description in in- and exclusion criteria
  Systematic reviews are characterized by having clear predefined eligibility criteria for which studies are included and excluded (4).
   
• Literature searching
  A systematic literature search is an essential part of a systematic review and forms the basis for data collection. See Literature Searching - Systematic Literature Searching.

• Sorting and selection of literature
  Based on the predefined qualification criteria, the searched studies are selected for further analysis. See Sorting and Selection and Reference management Tools.

• Extraction of data and ctitical assessment of included studies
  The quality of evidence is assessed according to the type of study, see Extraction and quality assessment.

• Evidence synthesis
  The Evidence synthesis includes a qualitative analysis (methodological description of the included studies, strengths and limitations, (ref. 3), and if possible, a quantitative analysis meta-analysis).

PRISMA statement (Preferred Reporting Items for Systematic reviews and Meta-Analyses) is a reporting guideline that includes a number of steps that should be included and reported when preparing and reporting systematic reviews and meta-analyses. See Reporting and PRISMA.

1. Cumpston M, Flemyng E, Thomas J, Higgins JPT, Deeks JJ, Clarke MJ. Chapter I: Introduction. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook

2. Campbell Collaboration: Better evidence for a better world.

3. Institute of Medicine of the National Academies. Standards for Systematic Reviews (2011).

4. McKenzie JE, Brennan SE, Ryan RE, Thomson HJ, Johnston RV, Thomas J. Chapter 3: Defining the criteria for including studies and how they will be grouped for the synthesis. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.4 (updated August 2023). Cochrane, 2023. Available from www.training.cochrane.org/handbook.

In addition to the literature referenced under References (above), you can read more in:
Cochrane handbook for systematic reviews of interventions. (2024). (J. Higgins, J. Thomas, J. Chandler, M. Cumpston, T. Li, M. Page, & V. Welch, Eds.). Cochrane. https://training.cochrane.org/handbook/current 

Cochrane Interactive Learning Module 3: Searching for studies
(Only access with SDU E-mail by creating an account. Module with self-training on the process with systematic searching)

See References on conceptualization models

• Baudard, M., Yavchitz, A., Ravaud, P., Perrodeau, E., & Boutron, I. (2017). Impact of searching clinical trial registries in systematic reviews of pharmaceutical treatments: methodological systematic review and reanalysis of meta-analyses. BMJ, 356, j448. https://doi.org/10.1136/bmj.j448  
• Bettany-Saltikov, J., & McSherry, R. (2016). How to do a systematic literature review in nursing: a step-by-step guide (Second edition ed.). McGraw Hill Open University Press.
• Bramer, W. M., de Jonge, G. B., Rethlefsen, M. L., Mast, F., & Kleijnen, J. (2018). A systematic approach to searching: an efficient and complete method to develop literature searches. Journal of the Medical Library Association, 106(4), 531-541. https://doi.org/10.5195/jmla.2018.283 
• Faggion, C. M., Jr., Huivin, R., Aranda, L., Pandis, N., & Alarcon, M. (2018). The search and selection for primary studies in systematic reviews published in dental journals indexed in MEDLINE was not fully reproducible. Journal of Clinical Epidemiology, 98, 53-61. https://doi.org/10.1016/j.jclinepi.2018.02.011 
• Frandsen, T. F., Dyrvig, A. K., Christensen, J. B., Fasterholdt, I., & Oelholm, A. M. (2014). [A guide to obtain validity and reproducibility in systematic reviews] [A guide to obtain validity and reproducibility in systematic reviews.]. Ugeskrift for Læger, 176(7), 647-651. https://www.ncbi.nlm.nih.gov/pubmed/25096352 
• Institute of Medicine. 2011. Finding What Works in Health Care: Standards for Systematic Reviews. Washington, DC: The National Academies Press.
• JBI Manual for Evidence Synthesis. (2020). (E. Aromataris & Z. Munn, Eds.). The Joanna Briggs Institute. https://doi.org/https://jbi-global-wiki.refined.site/space/MANUAL 
• Khan, K. S. (2011). Systematic reviews to support evidence-based medicine: how to review and apply findings of healthcare research (2 ed.). Hodder Arnold.
• Koffel, J. B., & Rethlefsen, M. L. (2016). Reproducibility of Search Strategies Is Poor in Systematic Reviews Published in High-Impact Pediatrics, Cardiology and Surgery Journals: A Cross-Sectional Study. PloS One, 11(9), e0163309. https://doi.org/10.1371/journal.pone.0163309 
• Laursen, D. R. T., Brorson, S., Lundh, A., Moller, A. M., Nejstgaard, C. H., Rosenberg, J., & Hrobjartsson, A. (2024). Kritisk læsning af systematiske oversigtsartikler. Ugeskrift for Laeger, 186(13). https://doi.org/10.61409/V09230616 (Critical reading of systematic review articles.) 
• McGowan, J., Sampson, M., Salzwedel, D. M., Cogo, E., Foerster, V., & Lefebvre, C. (2016). PRESS Peer Review of Electronic Search Strategies: 2015 Guideline Statement. Journal of Clinical Epidemiology, 75, 40-46. https://doi.org/10.1016/j.jclinepi.2016.01.021  
• Meert, D., Torabi, N., & Costella, J. (2016). Impact of librarians on reporting of the literature searching component of pediatric systematic reviews. Journal of the Medical Library Association, 104(4), 267-277. https://doi.org/10.3163/1536-5050.104.4.004  
• What is a systematic review? (2023).  Cambell Collaboration. https://www.campbellcollaboration.org/what-is-a-systematic-review.html

Qualitative Systematic Reviews:

• Booth, A. (2016). Searching for qualitative research for inclusion in systematic reviews: a structured methodological review. Syst Rev, 5, 74. https://doi.org/10.1186/s13643-016-0249-x
• Frandsen, T. F., Gildberg, F. A., & Tingleff, E. B. (2019). Searching for qualitative health research required several databases and alternative search strategies: a study of coverage in bibliographic databases. Journal of Clinical Epidemiology, 114, 118-124. https://doi.org/10.1016/j.jclinepi.2019.06.013
• Munn, Z., Stern, C., Aromataris, E., Lockwood, C., & Jordan, Z. (2018). What kind of systematic review should I conduct? A proposed typology and guidance for systematic reviewers in the medical and health sciences. BMC Medical Research Methodology, 18(1), 5. https://doi.org/10.1186/s12874-017-0468-4