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Systematic review guide

A step by step guide to doing a systematic review

Search strategy design

The search is the backbone of the review - any relevant material missed due to poor searching could seriously influence the quality and relevance of the review. Search is vulnerable to introducing bias into the review and as such, the methods for systematic search are designed to reduce bias where possible. 

Systematic searching differs from the traditional narrative literature review search. It must be: 

  • Thorough: more than one database should be used and a combination of textwords plus subject headings (when available) to identify relevant literature. Supplementary search methods are likely to be required in addition to database searching. An appropriate range of other information sources should be used to find relevant literature beyond journal articles such as policy documents, reports or registered trials, depending on the research area. 

  • Objective: search terms. Include variations in terminology and the searcher should avoid biasing the results of the search through a narrow selection of textwords and subject headings. 

  • Reproducible: the searcher must record all the details of the search, including the databases and database platform with dates of coverage, the search strategy and the date each search was run. This allows for transparency of your search methodology via reporting as required by PRISMA and other reporting standards.

A good systematic search will be comprehensive and exhaustive and will prioritise sensitivity over specificity. 
The right balance of sensitivity and specificity will minimise "noise" (correctly identified yet irrelevant results) where possible, but not at the expense of potentially missing other relevant results. This will involve:

  • A complete range of search terms for each search concept via textword and subject heading searches (not just some relevant terms)
  • A range of relevant databases, sources and supplementary search techniques 
  • An iterative approach, creating, evaluating and tweaking the strategy as you become more familiar with the literature it finds