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Search strategies for systematic reviews

Systematic searches

  • Create you search with the help of search blocks
  • The search blocks should contain both subject headings and free text words (when applicable)
  • Run your search in several databases with a similar search string
  • Will get you a search result where you can go through the whole list of studies
  • Is so transparent and well documented which makes it possible to repeat

Choose your databases

Subject specific databases

Interdisciplinary Databases

Databases with content in languages other than English

To find all studies in a field, you may need to search outside the traditional English-language sources.

Create a search strategy - Step by step

Before you start your searching

  • Have you already found relevant studies?
Search for the studies in one of the selected databases and document which keywords are used in the title and abstract as well as which subject headings/descriptors they have been indexed with, which are relevant to your search.

Do a test search

  • Have you done a test search?
Do a test search in one of the databases (if you know which one will be most important, start in that one). The search does not have to be comprehensive. Document words in title, abstract, key words and subject headings.
  • Have you found a literature review?

Have a look to see how they have reported their search strategy,  you can document the words in the title, abstract and subject words that are relevant to your search.

  • Have you found relevant studies in your test search?
Keep searching to see if you can find more relevant subject headings, key words and concepts. Make a note when you find new ones. You can change your search strategy when you find new keywords. Also look if the database provides information about similar articles, which can be called "Similar articles", "Related articles" etc.

Use search filters

  • Have you found any search filters?
Search filters are search strategies designed to capture a certain aspect, such as study design. There are search filters that are validated, tested against a gold standard of relevant articles to make sure that these are captured by the search filter. The aim is to find a search strategy that captures as many relevant studies as possible while limiting the number of irrelevant studies. The search filters are designed to fit different databases. There are search filters for study design, age, geography etc.

ISSG Search Filter Resource

CADTH Search Filter Database

SIGN Search Filters

What is a controlled vocabulary?

In many of the subject databases the article content is described using a controlled vocabulary, thesaurus. A concept can be described with different synonyms, but the controlled vocabulary is set.

Example:

Heart attack

Studies ont heart attack, using different words to describe it, will be tagged with the subject heading Myocardial infarction. Thus searching the subject heading will retrieve articles using different synonyms, but they have all been tagged with the same subject heading.

Synonyms Subject Heading
Heart attack Myocardial infarction
Heart infarction  
Cardiac arrest  
Cardiovascular disease  
Myocardial infarction  

Note that the interdisciplinary databases like Web of Science or Scopus doesn't have a controlled vocabulary

How to search with boolean operators

At least one of the words should be included in the search - OR

OR indicates that one or more words should be included in the search. Use OR to search for both the words as subject heading and free text words or on synonyms and related terms. You get more results and do a more exhaustive search.

Nurses[Subject Heading] OR nurses

All the words must be included in the search - AND

AND indicates that all keywords or search blocks that you combined should be included in the search. You get fewer but more relevant hits.

(Nurses[Subject Heading] OR nurses) AND (covid-19 OR sars-cov-2)

Search for parts of a word - truncate

Truncation means shortening a word to its word stem and then putting an asterisk (*) which indicates that different endings, inflections and spellings of a word should be searched for.

nurse* (searches for nurse, nurses etc.)

Phrase search - search for phrases or concepts - citations

When you want to search for terms that contains two or more words. Specifies that the words are to be searched together in the exact order and with the spelling that is written. You get fewer and more relevant hits.

"nursing care"

Example Search Strategy:

Nurses experience of psychological stress when caring for patients with covid-19

PEO

Population Nurses Nurse[Subject Heading] OR nurse[Free text word] OR nurses[Free text word]
Exposure Caring for patients with Covid-19 Covid-19[Subject Heading] OR SARS-CoV-2[Subject Heading] OR covid-19[Free text word] OR SARS-CoV-2[Free text word]
Outcome Psychological stress Stress, Psychological[Subject Heading] OR psychological stress[Free text word] OR burnout[Free text word]

Search string

(Nurse[Subject Heading] OR nurse[Free text word] OR nurses[Free text word])  AND (Covid-19[Subject Heading] OR SARS-CoV-2[Subject Heading] OR covid-19[Free text word] OR SARS-CoV-2[Free text word]) AND (Stress, Psychological[Subject Heading] OR psychological stress[Free text word] OR burnout[Free text word])