Library Guides: Systematic Review: Search techniques

Key techniques

Use the following techniques when entering your search terms into databases to help you find relevant results:

Phrase searching

Command	" " vertical quote marks (be careful with copy and paste)
Use	To enclose a short phrase
Effect	The search will find the exact phrase
Example	"mental health"

Truncation

Command	* asterisk (in most databases) A few databases truncate word stems automatically.
Use	On the end of a base/root word
Effect	The search will find all the different word endings
Example	teen* finds teen, teens, teenage, teenager, teenagers, teenaged

Combining search terms

OR

Use between search terms describing one concept to find results containing any of the alternative terms.

Using OR broadens your search.

Example: "vitamin C" OR "ascorbic acid" will find records with one of these terms or both.

AND

Use to combine your concepts to only find results containing all the concepts.

Using AND narrows your search.

Example: "pain management" AND "mobile applications": both terms must be present in the results.

NOT

Use to exclude terms from your search results.

Using NOT narrows your search.

Example: diabet* NOT gestational: records that have the term "gestational" are excluded from the results.

Combining operators

When using a combination of AND and OR operators in a search, enclose the alternative terms or synonyms in parentheses.

Example: ("vitamin c" OR "ascorbic acid") AND (cold OR flu OR influenza)

See Search strings for more details.

Useful tools

PubVenn - explore PubMed using venn diagrams to find the relative size of the citation set for each term as well as how those sets interact. These diagrams may help users visualize how complex searches work.

Proximity searching

This search technique is occasionally helpful for finding relevant results:

Command	N# (EBSCO) ADJ# (OVID) W/# (Scopus ) Note: # is a number
Use	Links two terms together (where a relationship between the 2 elements is inferred)
Effect	The search will find the first term only if it is located within a maximum number of words of the second term. The order of the terms is not important.
Example	EBSCO: (diabet) N6 (foot OR feet) OVID: (diabet) ADJ6 (foot OR feet) Scopus: (diabet) W/6* (foot OR feet)

Proximity searching narrows your search

It is especially good for searching keywords within full-texts
Not all databases are capable of proximity searching

Subject Headings

Most databases have subject headings (controlled vocabularies) assigned to articles to describe what the article is about.

Subject headings are database specific
Subject headings yield precise results
If you use subject headings, you will also need to include keywords for the concept in your search
Check Scope notes for details on what the subject heading covers.
Consider whether to use Explode or the Subheading options where they are available

Examples of subject headings used in some key databases:

Databases	Subject Headings
AMED	AMED Thesaurus
Business Source Complete	Business Thesaurus
CINAHL	CINAHL Headings; MeSh
EMBASE	EMTREE
MEDLINE	MeSH
PsycINFO	PsycINFO Thesaurus; MeSh

MeSH (Medical Subject Headings)

MeSH is a well-known thesaurus of biomedical and health related information.

You will find MeSH in the Medline database, via EBSCO, OVID, PubMed or Web of Science.

Search Mesh headings using MEDLINE (EBSCO)

Yale MeSH Analyzer

The Yale MeSH analyzer (by the Yale University Library) allows users creating a MeSH analysis grid using PubMed. Use it to identify new search terms and the missing articles from PubMed.

Video tutorial: Yale MeSH Analyzer (7.39 mins).

MEDLINE (OVID) Expand Term Finder

Search MeSH headings, Stedman's Medical Dictionary and related terms from the Unified Medical Language System (UMLS)
Explore MeSH headings: MeSH tree, used for terms, scope notes, subheadings
Expand Term Finder is only available for MEDLINE currently

Find more information in OVID's online guide and video

OVID Search Builder

A new OVID search tool allows users to:

combine keywords, MeSH headings and synonyms in one search
apply multiple keywords in a PICO format
use specialised filters to search for adverse events, special situations and clinical queries
search across MEDLINE and Embase databases

Video: Ovid Search Builder (9.28mins).

Snowballing

Snowballing refers to using the reference list and the citations of papers you have selected for your research to identify additional papers. It involves looking backwards and forwards to identify other papers that may be relevant. This allows capture of papers that may not appear in search results due to keywords or terminology not used or indexed in a database.

Backward snowballing

Use the final set of selected papers from your systematic searching
Scan the titles in the reference list in each paper
Examine those that may be useful using your inclusion/exclusion criteria
Add relevant papers to your list selected for review if they are not included already

Forward snowballing

Examine the papers citing each paper in your final set of papers
Use your inclusion/exclusion criteria to determine if they are useful - check the title, abstract, then full text
Add the papers to your list selected for review if not included already

Tools

Find citations for the papers in Scopus, Google Scholar or any other resources. Citation analysis tools are available in Scopus.

Other tools may also be used for citation analysis (e.g. for finding themes, how articles cite each other, and gaps):

Vosviewer
OVID Citation Analyzer
Microsoft Excel

Systematic Review