Knowledge Synthesis: Systematic, Scoping & Other Reviews

Many databases include a system of subject headings (which may also be called descriptors, or controlled vocabulary). These terms are added to articles by human indexers to make it easier to search for all the articles on a particular concept. Most other topical, or subject, databases have a system of subject headings, which can usually be found in the thesaurus section of a database. In Medline these are known as MeSH (Medical Subject Headings), in EMBASE as Emtree, and in CINAHL they are Headings.

For a thorough literature search, you should search each concept with both keywords and subject headings.

Some databases and grey literature sources only allow searching by keyword (aka free text or natural language). Useful techniques include truncation, wildcards, phrase searching, and proximity searching.

The table below summarizes various search techniques across a selection of databases and search tools.

NOTES AND EXPLANATIONS

[xix] Truncation and wildcards cannot be used with phrase searching or proximity searching. https://help.cabi.org/cabi-digital-library-help/search/truncation-or-using-wildcards-for-searching-with-partial-search-terms

[xx] https://help.cabi.org/cabi-digital-library-help/search/using-double-quotes-for-exact-matching-of-words-and-phrases  

[xxi] Place quotation marks around the terms you want to search for, followed by a tilde ~ and a number indicating the maximum number of words separating the terms.  If a proximity operator is included inside double quotes “~” it is ignored https://help.cabi.org/cabi-digital-library-help/search/proximity-searching

[i] In OVID databases, you must turn off Subject mapping for truncation to work. You may add a number after your truncation symbol (i.e., *5) to restrict the search to a certain number of characters. For instance, the search: fish*4 would find fish, fishes, fishing, etc., but would not find longer results, such as “fisheries”.

[ii] In OVID databases, use the ? wildcard symbol to find variations of spelling for the term. The ? symbol is used inside or at the end of the search word. For instance colo?r would find all results for "color", and all results for "colour". And bird? Would find results for "bird" and "birds".

[iii] In OVID databases, use the # wildcard symbol to find variant spellings of a word. It can be placed inside or at the end of a search word. The # symbol must replace exactly one character (i.e., wom#n). So if you searched for: colo#r it would only find results for “colour”, but not color.

[iv] In OVID databases, you may broaden or narrow your search by using the proximity searching operator Adj with a number 1-99. e.g. adj3 searches for terms within 3 words of each other in any order. ADJ without a number finds terms next to each other in specified order. http://site.ovid.com/site/help/documentation/osp/en/Content/syntax.htm#operators

[v] To create a wildcard search in PubMed, use an asterisk (*) to substitute for 0 or more characters in a term or phrase. In PubMed using the * truncation symbol will prevent subject mapping of your search term. In PubMed using the * truncation symbol will prevent subject mapping of your search term. It will find the first 600 possible results and then stop searching. https://pubmed.ncbi.nlm.nih.gov/help/#wildcards

[xxii] When you enter search terms as a phrase, PubMed will not perform automatic term mapping that includes the MeSH term and any specific terms indented under that term in the MeSH hierarchy. For example, "climate change" will include citations that are indexed to the MeSH term, Climate Change, but will not include the more specific terms, e.g., Global Warming or Sea Level Rise https://pubmed.ncbi.nlm.nih.gov/help/#searching-for-a-phrase

[xxiii] Does not work with the “All Fields” field code; limited to [Affiliation], [Title] and [Title/Abstract] fields. https://pubmed.ncbi.nlm.nih.gov/help/#proximity-searching

[vi] In PROQUEST databases, you may add a number after your truncation symbol (i.e., *5) to restrict the search to a certain number of characters. For instance, the search: fish*4 would find fish, fishes, fishing, etc., but would not find longer results, such as "fisheries".

[vii] In PROQUEST databases, use the ? wildcard symbol to replace any single character, either inside or at the end of the search word. Multiple wildcards can be used to represent multiple characters. For example: nurse? would find: nurses, nursed, but not nurse; sm?th would find: smith and smyth; ad??? would find: added, adult, adopt.

[viii] In PROQUEST databases, use NEAR/n or N/n to look for documents that contain two search terms, in any order, within "n" specified number of words apart. Replace "n" with a number. For example: nursing NEAR/3 education; media N/3 women.

[ix] Use PRE or P to search for a term within specified number of words before a second term. Eg: nursing PRE/4 education

[x] Use # for alternate spellings. For example, colo#r finds – color/colour.

[xi] In EBSCOHOST databases, use the ? wildcard to find an unknown character. For example, type ne?t to find all citations containing neat, nest or next. EBSCOhost does not find net because the wildcard replaces a single character.

[xii] In EBSCOHOST databases The N5 proximity search finds the words if they are within five words of one another regardless of the order in which they appear. The W5 proximity search finds the words if they are within five words of one another and in the order in which you entered them.

[xiii] In Engineering Village, Inspec database, search term stemming is automatic. Using truncation or wildcard characters automatically turns the “auto-truncation” off. You may also turn it off by selecting “auto-stemming>off”. To turn truncation off when not using a truncation or wild card character, put search terms in between quotation marks or braces {}. You may use the * truncation character at the beginning or end of a search term.

It also can be used as a mutli-character wildcard. Use an asterisk to replace 0 to X number of characters anywhere in the word.  

Examples:

• h*emoglobin finds hemoglobin, haemoglobin, hemimethemoglobin
• Sul*ate finds sulfate, sulfonate, sulphate, sulphonate.  

Left Truncation: If you precede a word with the an asterisk *

Example:

• *sorption returns adsorption, absorption, chemisorption, desorption, resorption, sorption

[xiv] ONEAR finds words in proximity to one another, in exact order entered.

[xv] In Web of Science databases you can use truncation in Title or Topic searches. You must enter at least three characters before and after a wildcard when using either left-hand truncation or right-hand truncation.

[xvi] The asterisk (*) represents any group of characters, including no character.The question mark (?) represents any single character.The dollar sign ($) represents zero or one character.

[xvii]

• In PEDro, truncation at the end of a word is automatic.
• If you would like to truncate the beginning of the word - for example, if you wanted to find papers on edema, oedema, lymphedema or lymphoedema, type *edema in a text field. Note, that if you put an asterisk * at the beginning of a word, PEDro will not also find variants at the end of the word (that is, PEDro can’t simultaneously search for variants at the beginning and end of the same word).

[xviii] In Google, there are some additional wild cards you can use:#Search for specific types of files, such as PDFs, PPTs, or XLS, by adding filetype: and the 3-letter file abbreviation.

1. Add a tilde sign (~) immediately in front of a word to search for that word as well as even more synonyms.
2. Use the related: operator to find pages that have similar content by typing related: followed by the website address. For instance, if you find a website you like, try using related:[insert URL] to locate similar websites.
3. If you want to search for pages that may have just one of several words, include OR (capitalized) between the words. Without the OR, your results would typically show only pages that match both terms. You can also use the | symbol between words for the same effect.
4. Include site: to search for information within a single website like all mentions of "Olympics" on the New York Times website. [ Olympics site:nytimes.com ]
   Tip: Also search within a specific top-level domain like .org or .edu or country top-level domain like .de or .jp.
5. Add a dash (-) before a word to exclude all results that include that word. This is especially useful for synonyms like Jaguar the car brand and jaguar the animal.[ jaguar speed -car ].

[xxiv] https://blog.scopus.com/posts/6-simple-search-tips-lessons-learned-from-the-scopus-webinar  

Preceding (Pre/n): The first word must be no more that (n) words apart from the second word

zika Pre/2 virus

This will find literature where ‘zika’ precedes ‘virus’ within 2 words, such as both “zika virus” and “zika and dengue virus”

Within (W/n): It doesn’t matter which word comes before the other  

zika W/2 virus

This would look for ‘virus infection with zika,’ ‘Virus like zika,’ ‘virus, zika,’ ‘zika virus,’ etc.

Information in this guide is based on database and search engine help pages.

File:Library Truncation and wildcards handout 2013.pdf

Credits: ^[1]

1. ↑ Beck, Charlotte and Longley, Kate, UBC Library. 2012 [online]. Truncation and Wildcard Symbols. Available from http://wiki.ubc.ca/Library:Truncation_and_Wildcard_Symbols  This work Truncation and Wildcard Symbols, by Charlotte Beck and Kate Longley, identified by UBC Library, is free of known copyright restrictions.
   
   
   Creative commons license

Boolean operators are useful for combining subject headings and keywords.

• Example: Stroke AND balance finds articles with both these concepts
• Example: Stroke OR CVA finds articles that include either or both concepts

NOT is another operator which will find one concept while excluding another. Use with caution because you may exclude relevant articles this way. See the document below for tips.

Most databases include various limiters. These usually qualify human characteristics such as gender, ethnicity or age or publication characteristics such as language, publication date, study design, or type of publication. 

Consult with a librarian about using limits in a systematic review search - it's easy to lose relevant articles when adding limits. Usually a search filter (aka hedge) is a better choice than using the default limits in a database. A search filter includes a mix of keywords and limiters.

For further discussion, see: Cochrane Handbook Chapter 4.4.5: Language, data and document format restrictions