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Evidence Syntheses and Systematic Reviews: Analyze and Report

Analyze

Deduplicating

Searching multiple databases generally mean that you will end up having duplicate results. Citation managers like RefWorks and Zotero can help with removing these duplicates. It is is important to always keep track of the number of citations before and after deduplicating, as that information has to be included in your final report.

Screening the Articles

The inclusion and exclusion criteria you developed will help you remove articles that are not relevant to your topic. This is usually a two-step process.

  1. Screen title/abstract of citations.
  2. Review the full text of the articles to make sure that the study definitely meets the eligibility criteria that you had selected.

It is recommended that more than one person be involved in this step, and if there's a need to resolve disagreements, a third party, usually an expert in the field, can be brought in.

Assessing the Risk of Bias

For systematic reviews, assess the quality of your findings to eliminate bias in either the design of the study, or in the results/conclusions of individual studies. This is sometimes referred to as "quality assessment" or "critical appraisal".

Data Extraction

There are several tools used to extract the data from the final articles selected for your study. Excel is the most basic tool for the management of the screening and data extraction stages of the systematic review process. 

Synthesize

After extracting the data, you can summarize and synthesize the results. Summarizing means concisely discussing the important themes in your research, whereas synthesizing means taking information from a variety of sources, and coming up with something different and new.

Some studies are synthesized either qualitatively or quantitatively, or sometimes even, both ways. 

Qualitative synthesis involves describing your study, how the different studies relate, comparing and contrasting them. You have to discuss how the evidence in your study either validate or refute your original research question; identify the gaps in the evidence, and suggest other ideas for further research.

Quantitative synthesis combines and analyzes the results of your study using statistical methods.

Report

Writing up the report on systematic review needs to do be needs to be done in a clear and detailed manner, using the appropriate reporting guidelines.

Reporting guidelines normally provide a list of items to consider when reporting the results of your study. PRISMA  (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) - the most widely known, lists the following items that should be included when reporting the results of the study:

  • Study selection:  numbers of studies screened, assessed for eligibility, & included in the review, with reasons for exclusions at each stage, ideally with a flow diagram.
  • Study characteristics:  For each study, characteristics for which data were extracted (e.g., study size, PICOs, follow-up period) & citations.
  • Risk of bias within studies:  data on risk of bias of each study &, if available, any outcome level assessment.
  • Results of individual studies:  For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group  (b) effect estimates & confidence intervals, ideally with a forest plot. 
  • Synthesis of results:  results of each meta-analysis done, including confidence intervals & measures of consistency.
  • Risk of bias across studies:  results of any assessment of risk of bias across studies.
  • Additional analysis: results of additional analyses, if done (e.g., sensitivity or subgroup analyses, meta-regression).

When selecting a journal to submit the report to, it is best to choose a journal, or avenue for publication that will provide the greatest exposure for the study.