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Evidence Synthesis

A guide to evidence synthesis methods such as systematic reviews, scoping reviews, and structured literature reviews.

Planning Worksheet

Planning Worksheet for Structured Literature Reviews

https://osf.io/ezqpd/

Steps

1) Formulate a solid research question

  • It will be much easier for you to perform a structured information search if you first define and delimit your research question in a clear way.
  • One way to define and structure your question is to break it down into different parts.
  • PICO and PEO are two different frameworks that can be used for breaking down a research question into different parts.
  • You also need to define the most important key concepts of your research question.

The more specific and focused your research question is, the easier the research will be. Consider using PICO - Population, Intervention, Comparison, Outcome or PEO - Population, Exposure, Outcome to think through and narrow down your research question.

2) Find Search Terms and Make Search Concept Blocks

  • Test searching is a good way to investigate the terminology of a subject area and find search terms.
  • Reading key articles can help you gather additional search terms for your final search strategy.
  • Find subject headings for PubMed with the help of the US National Library of Medicine's MeSH database.
  • Find& free-text search terms by investigating what words that occur in the title and abstract of relevant articles.
  • A good way of achieving a structured final search query is to arrange your search terms into search blocks; these blocks should arise from the key concepts of your research question.

3) Search in a Structured Way and Document Your Searches

  • To get a comprehensive search result, you will need to search for articles in several different databases.
  • Your search strategy should be as uniform as possible in every database, but you may have to adapt your use of subject headings.
  • As you search the databases, combine your search terms and blocks with the help of AND and OR.
  • Save time by documenting your search queries (documentation template)

4) Narrow or Broaden Your Searches

  • Briefly examine your search results to see if you need to narrow or broaden your search query.
  • Investigate whether your key articles are present in the search results.
  • By using the advanced search form you can improve your search.

Remember, searching is iterative - you may likely will need to refine multiple times. Be transparent and document every decision you make about refining your search strategy.

  • Are all your key articles present in the search results, or are there some key articles that your search query is unable to retrieve?
  • Are you getting too few search hits? Investigate why. Perhaps you need to remove one of your search blocks, add one or several synonyms within a search block, or search for parts of words by truncating one or several of your free-text search terms, in order to broaden your search?
  • Does your search strategy generate too many non-relevant search hits that have nothing to do with your research question? Investigate why. Perhaps you need to add another search block, remove one of the synonyms from one of your search blocks, or search for phrases by enclosing one or several of your free-text terms in quotation marks, in order to narrow your search?
  • More tips on how to improve your search strategy.

5) Select and Review Articles

  • After you have completed your search, you will need to go through all your search hits and select which articles to include in your review.
  • When selecting articles, read through the titles and abstracts of each article to decide its relevancy.
  • Check the quality of each study that you include in your review.
  • When checking the quality of articles, it is common to use critical appraisal worksheets or checklists.

Most databases allow you to save/ export searches. You may need to sign up for a personal account in order to do so.

There are many different types of tools & methods you can use for Critical Appraisal. Review worksheets and checklists contain criteria and questions that may help you identify flaws, errors, or bias. Sometimes different aspects of the study are scored separately. Later, all scores make up a final score that indicates whether the study is of high, medium, or low quality.

6) Report Your Search Strategy

  • Describe your search strategy in a manner that makes it possible for your readers to replicate the search and get the same results.
  • The search strategy is often presented in the form of a table.
  • Look at the search history to see what words and limits that you have used when searching a database.

From: Structured literature reviews – A guide for students CC-BY-SA 4.0

7) Provide Critical, Thematic, Narrative Summary/ Analysis of the Literature

As well as finding and evaluating the given research on a question or topic, a literature review should demonstrate knowledge of the subject by engaging in some or all of these analyses:

  • Make connections between the sources, and demonstrate you understand their relationship to each other and larger conversations related to your research question
  • Identify key themes or trends and organize them in a logical manner
  • Apply or introduce a framework for understanding the research on the subject
  • Draw conclusions and make recommendations from the evidence presented
  • Identify gaps and areas for future research

From: https://libguides.westminster.ac.uk/literature-reviews/criticality

Critical and Comprehensive Literature Review Characteristics

Timeframe/ Resources

~1-6 months, bulk of time is spent reading resources & critically analyzing.
Single person

Purpose/ Type of Question

Provides summarization of recent or current literature. Can cover wide range of subjects at various levels of completeness and comprehensiveness.

Sources/ Searches

May include exploratory search strategies rather than strict protocols; should take advantage of Boolean and controlled vocabularies. May include articles, books, theses, and other sources.

Inclusion/Exclusion & Appraisal

May or may not include quality assessment. Typically less analysis of quality in favour of objective summarization. Can be transparent and intentional in inclusion/ exclusion.

Synthesis/ Reporting

Descriptive summary of the findings, may be organized thematically or chronologically.

Limitations

No formal structure/ reporting requirement on methods 

Interpretative, subjective, high risk of bias 

No necessary quality assessment/ tests for validity of included studies


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