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Systematic Reviews: Keywords

Overview of systematic review methodology and key strategies for searching and reporting to the Cochrane Collaboration's Gold Standard

Heading: Keywords

Keywords overview

It is best practice to search using both keywords and subject headings.

Move through the slide deck below to learn how to use keywords in your search. Alternatively, download the PDF document at the bottom of this box.

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Limiting your search by field

Database records contain descriptive information about publications organised into searchable sections called 'fields'. Targeting your search to specific fields can be a powerful tool when designing your search strategy.

By default, most databases will search for the terms you enter in a variety of fields. For example, in Ovid MEDLINE you will see

mp. [mp=title, abstract, original title, name of substance word, subject heading word, floating sub-heading word, keyword heading word, organism supplementary concept word, protocol supplementary concept word, rare disease supplementary concept word, unique identifier, synonyms]

Here, mp stands for 'multi-purpose'.

You may be able to improve the relevancy of your results by searching for terms in specific fields.

Recent change (Sept 2021): Embase now aligns with MEDLINE with .kf for author supplied keywords

Commonly used fields for systematic reviews: databases available via Ovid (selection)

Database Title Abstract Author supplied keyword Textword - combined fields
MEDLINE .ti .ab .kf .tw (includes Title and Abstract)
Embase .ti .ab .kf .tw (includes Title, Abstract, and Drug Trade Name)
Emcare .ti .ab .kw n/a
PsycInfo .ti .ab n/a .tw (includes Table of Contents, Title, Abstract and Key Concepts)

How to use field codes - example searches:
chronic pain.tw
(chronic pain OR recur* pain).tw - use brackets when combining terms
(chronic pain OR recur* pain).ti,ab. - use a comma to combine fields

For a full breakdown of all available fields within any Ovid database click the 'i' icon to the left of the database name which will take you to the Field Guide for your selected database:

Image of 'i' icon within MEDLINE database

Guidelines and standards

‘If natural language processing or text frequency analysis tools were used to identify or refine keywords, synonyms, or subject indexing terms to use in the search strategy, specify the tool(s) used.’ - PRISMA 2020 Explanation and Elaboration, p. 7


Other standards

Key guides

Mining for keywords

When developing a comprehensive list of keywords, the following tools may be useful to explore: