Systematic reviews

A systematic review is a methodologically rigorous method of undertaking a literature review. The aim for a review of quantitative evidence is usually to arrive at an estimate of effect (or possibly a range of estimates) in order to answer a focused research question. It is normally expected that a dissertation based on a systematic review includes the following:

• a focused and feasible research question, expanded into aims and objectives as appropriate;

• background section explaining the topic and justification of the need for the review;

• methods section incorporating justification of review methods and citing of appropriate methodological literature, with sub-sections that include:

  • • pre-specified selection criteria for primary studies;

    • a comprehensive search strategy;

    • description of standardised data collection for each included study;

    • description of standardised methodological assessment for each included study;

    • description of a structured data synthesis (which may be a narrative synthesis, meta-analysis, or a combination of both).

• results section which should include the following:

  • • results of search strategy;

    • description of primary studies including summary of methodological quality;

    • narrative synthesis of findings

    • where possible and appropriate estimates of effect for all pre-specified outcomes

    • assessment of risk of bias using validated tools (e.g. Cochrane RoB-2)

• discussion section which should include a summary of main findings, an account of resolution/remaining uncertainty in relation to the review question, quality of evidence, strengths and limitations of the review, context of findings in relation to existing literature, recommendations for future research and clinical or other professional practice or implications for public health, and concluding comments.

• there must be evidence of critical and analytical treatment of primary material throughout the dissertation

• review methods, processes, and findings must be reported in a transparent way.

Many people believe that systematic reviews can only be based on randomised controlled trials (RCTs). Since a systematic review is essentially a set of scientific principles, the method can be applied to any type of primary study design, including observational studies, qualitative studies and others. Systematic review may also be used to address methodological questions; Whatever the focus of the review, the question, rationale, methods and findings need to be reported in a transparent fashion.

Example research questions:

• What is the effectiveness of preoperative statin therapy in patients undergoing cardiac surgery?

• What is the impact of indoor residual spraying alone, and what are the relative impacts of indoor residual spraying and insecticide-treated mosquito nets, on key malariological parameters?

• What is the effectiveness, and what are the adverse effects of acupuncture in the treatment of depression?

• How can school-based interventions prevent HIV, sexually transmitted infections and pregnancy in adolescents?

All of the above questions are taken from systematic reviews which can be accessed from the Cochrane Library.

Example research questions for methodological systematic reviews:

• What is the impact of attrition on estimates of treatment effect?

• What is the impact of inadequacy of treatment allocation on estimates of treatment effect?

At this level, it is not expected that the studies identified will be assessed by a second reviewer, however, the supervision team may be asked to screen up to 10 papers. 

Furthermore, as per the information on the PROSPERO site, you do not need to register your study:

 “PROSPERO has limited resource and is unable to process student work done as part of their training. Students may use the system to create and store a record by saving but please do not submit. Substantial reviews done for dissertations or theses may be registered but will require email confirmation by supervisors”.  

Useful references:

• Cochrane Handbook for Systematic Reviews of Interventions. Available from http://training.cochrane.org/handbook (accessed February 2024)

• Systematic Reviews: CRD’s guidance for undertaking reviews in health care. Available from http://www.york.ac.uk/inst/crd/index_guidance.htm (accessed February 2024).

• Cochrane Interactive Learning Module 1: Introduction to conducting systematic reviews. Available from: https://training.cochrane.org/interactivelearning/module-1-introduction-conducting-systematic-reviews (accessed February 2024) – free but registration required

• IMPACT systematic review webinars developed in collaboration with Cochrane Common Mental Disorders (11 sessions, free). Available from: https://www.youtube.com/watch?v=Fn0jQ8vLcTw&list=PLKav5fAJIAOIzyzeZY7h0V3wJyXPkGTRc (accessed February 2024)

• SWiM (Synthesis Without Meta-analysis) Guidance. Available from: https://swim.sphsu.gla.ac.uk/ (accessed February 2024)

• PRISMA reporting standards for systematic reviews. Available from: http://www.prisma-statement.org/ (accessed February 2024)