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Systematic Reviews

What is a Systematic Review?

The PRISMA statement defines a systematic review as "a review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyze data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyze and summarize the results of the included studies. Meta-analysis refers to the use of statistical techniques in a systematic review to integrate the results of included studies." 1

In the Cochrane Handbook for Systematic Reviews of Interventions, the key characteristics of a systematic review are listed as:

  1. "a clearly stated set of objectives with pre-defined eligibility criteria for studies
  2. an explicit, reproducible methodology
  3. an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
  4. a systematic presentation, and synthesis, of the characteristics and findings of the included studies." 2
1. Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group. Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. PLoS Med. 2009;6(7):e1000097. https://doi.org/10.1371/journal.pmed.1000097
2. Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions, Version 6.1 (updated September 2020). Cochrane, 2020. Available from https://training.cochrane.org/handbook/current

Resources

Standards

Protocol

Register your protocol. Several options include:

Guidelines to Writing a Protocol

Searching

Article Databases

Grey Literature: Trial Registries

Organizing

Screening Tools

The Systematic Review Toolbox (SR ToolBox) is a searchable catalog of tools that support various tasks within the systematic review process. Tools include software tools, quality assessment / critical appraisal checklists, and reporting standards guidelines. A few of the featured tools are listed below, some free and some subscription-based. Many of the subscription-based tools offer a free trial if you are interested in exploring the tool.

Reviews of Screening Tools

Data Extraction

Data extraction is the process by which one extracts and records study characteristics and findings from each study included in the systematic review.  This information can be recorded in a spreadsheet or word processor. Or, use a software program such as Covidence, RevMan, or DistillerSR, or survey program such as Qualtrics or Google Forms. Use the SR Tool Box to search for other software tools.

What data, study characteristics, and information to extract from each study is unique to each review, but extracted data may include:

  • Article citation and funding sources
  • Study participants - demographics, characteristics of participants such as comorbidity, socio-economic status, ethnicity, etc. number of participants, recruitment procedures, details of randomization or blinding, etc.
  • Study methodology - study design, objectives of study, study inclusion and exclusion criteria, recruitment procedures, randomization and blinding, if applicable, etc.
  • Intervention and setting - description of the intervention, route of delivery, timing, equipment, dose, description of control group, etc.
  • Outcomes and results, quantitative and/or qualitative - whether the outcome was assessed and reported, unit of measurement, method of aggregation, tool used to measure outcomes,  adverse outcomes, costs, additional relevant outcomes

 

Data Extraction Tools

The Systematic Review Toolbox (SR ToolBox) is a searchable catalog of tools that support various tasks within the systematic review process. Tools include software tools, quality assessment / critical appraisal checklists, and reporting standards guidelines. A few of the featured tools are listed below, some free and some subscription-based. Many of the subscription-based tools offer a free trial if you are interested in exploring the tool.

Useful Readings

Appraisal

The Systematic Review Toolbox (SR ToolBox) is a searchable catalog of tools that support various tasks within the systematic review process. Tools include software tools, quality assessment / critical appraisal checklists, and reporting standards guidelines. A few of the featured checklists are listed below.

Risk of Bias

Books

Videos

The Brown University School of Public Health Evidence Synthesis Academy has developed a series of tutorials and videos about conducting systematic reviews.  Here is the introductory video:

The Steps of a Systematic Review

 According to the Cochrane website, "Our volunteers and contributors are researchers, health professionals, patients, carers, and people passionate about improving health outcomes for everyone, everywhere. Our global independent network gathers and summarizes the best evidence from research to help you make informed choices about treatment and we have been doing this for 25 years." This video defines a systematic review:

What are Systematic Reviews by Cochrane

The Systematic Review Process

  1. Define your research question
  2. Check to make sure a systematic review has not already been done on your topic. If one has been done, but it is old, contact the authors to learn whether they plan to update it
  3. Assemble your team. Team members may include subject specialists, a systematic review method specialist, a biostatistician (if a meta-analysis), and a librarian
  4. Develop your protocol and register it
  5. Search the literature and collect the results
  6. Screen titles and abstracts using your inclusion and exclusion criteria to identify potentially relevant studies
  7. Review the full text  of the articles chosen in step 6 to confirm eligibility 
  8. Appraise the quality of the eligible studies
  9. Extract the qualitative and/or quantitative data and synthesize
  10. Report the findings

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