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Systematic Reviews in the Health Sciences: Systematic Searching

Last Updated: Jun 6, 2022 1:05 PM

Search Strategies

Controlled vocabularies are standardized and organized arrangements of words and phrases used to describe data consistently. Also called subjects, subject headings or preferred terms, many databases have their own unique set. You may need to look for a dedicated search, dictionary or thesaurus within the database to discover the best terms for your search. A few well-known examples are below:

Example:

Teenager in MeSH maps to "Adolescent"[Mesh]. In Emtree, the preferred term is 'adolescent'/exp.

Keywords are the terms and their synonyms that you identify as relevant to your research question. You can build flexibility into your search by accounting for the different language researchers might use to describe the same topic. Careful consideration of terms will define the scope of your search.

Brainstorming terms and synonyms of those terms is a great place to start, but once you have a few articles that fit your research question, mine the language used by those authors for additional possibilities. Don't forget to include relevant international spellings (e.g. pediatric vs. paediatric) or even common misspellings.

Directing a database to search for keyworks in specific locations can help you improve relevancy of your results. Check for search field options to search within areas such as the title and/or abstract of an article. Each database is a little different, but check for drop-down menu next to search bars in an advanced search feature.

Example:

teen, teens, teenage, teenager, teenagers, adolescent, adolescents, adolescence, young adult, young adults

A high quality search is based not only on the selection of the correct terms, but how they are combined.

AND is the Boolean Operator used to combine unique concepts. Two terms combined with AND will only return matches that contain both concepts.

In the image below, the yellow circle represents all items in a database that involve the term 'chocolate'. The blue circle represents all items in a database that involve the term 'cake'. By searching for chocolate AND cake, the database will return only those results that are in the overlapping green area. This, for example, is where a recipe for chocolate cake would fall.

A Venn diagram with a yellow circle reading chocolate and a blue circle reading cake. AND is written in the overlapping area. An arrow is draw to this overlapping area with the text Chocolate Cake Recipe.

A high quality search is based not only on the selection of the correct terms, but how they are combined.

OR is the Boolean Operator used to combine synonymous concepts. Two terms combined with OR will return matches that contain any instance of either/all concepts.

In the image below, the yellow circle represents all items in a database that involve the term 'chocolate'. The pink circle represents all items in a database that involve the term 'strawberry'. By searching for chocolate OR strawberry, the database will return any results that contain either term. That means all results within either the yellow or pink areas.

A Venn diagram. A yellow circle reading chocolate overlaps with a pink circle reading strawberry. The word OR is above with a bracket encompassing both circles.

Keeping your unique concepts organized, use Boolean logic to combine your terms. The structure and punctuation used may look different across databases, but the basics are the same. AND combines to unique concepts and returns results that contain both. OR broadens your search by offering viable synonyms returning results that match any one of the terms. The basic structure is as follows:

(Concept1 OR Synonym1) AND (Concept2 OR Synonym2)

In the image below, the yellow circle represents all items in a database that involve the term 'chocolate'. The pink circle represents all items in a database that involve the term 'strawberry'. The blue circle represents all items in a database that involve the term 'cake'. By searching for (chocolate OR strawberry) AND cake, the database will return those results that involve either flavor and the term cake. These are represented in the overlapping purple, green and brown areas. In this example, you might get recipes for chocolate cake, strawberry cake and chocolate strawberry cake. You will not get tips on making chocolate covered strawberries.

Search Hedges

Hedges are standardized searches for particular databases that can improve the relevancy of your search results. They can also be called search filters, optimal search strategies, clinical queries, methodological filters or canned searches. There are many types of hedges covering particular populations, type of studies and more. Some hedges are validated for their sensitivity and specificity. You can review hedges to determine which might be best for your needs.

Search Translation

As systematic review require searching multiple databases, a systematic search will need to be translated to meet the syntax requirements and controlled vocabulary of each.

For example, in PubMed you might search for "ganglion cyst"[Title/Abstract] OR "Ganglion Cysts"[MeSH Terms] and retrieve over 1500 results.

But the same search copied and pasted into Embase will fail to run due to the syntax and punctuation used. Instead the PubMed search must be translated to into a search language Embase can understand: 'ganglion cyst':ti,ab OR 'ganglion cyst'/exp retrieves over 2200 results.

Tools such as the Systematic Review Accelerator's Polyglot can assist with this, but still require review for errors.

Tip: Pay attention to quotation mark requirements in different databases. PubMed uses "double straight quotes" but Embase only uses 'single straight quotes'. Curly or smart quotes should be avoided. They can be turned off in Word.

Grey Literature

The comprehensive and unbiased searching expected of a systematic review includes unpublished (grey) literature. This may include conference proceedings, theses and dissertations, and clinical trials. Combing report and conference proceedings hosted on relevant professional organization and conference websites might be included.

Video Help: Creating the Search for Systematic/Scoping Reviews

PRISMA-S

Key Databases

Health Sciences Research Guides