Tip #50: "Indexed Keywords" in Scopus: what they are, where they come from, and how (and whether) to exclude them
Scopus is a very large multidisciplinary database with a wide range of sources. According to Elsevier, almost 99% of journals indexed in Embase and MEDLINE are included in Scopus. Unlike Embase, which uses the Emtree thesaurus for indexing (the full Emtree thesaurus is only available in Embase), or MEDLINE, which uses MeSH (accessible publicly via the MeSH Browser or MeSH Database), Scopus does not have its own controlled vocabulary or thesaurus searching capabilities. So what are the "indexed keywords" in Scopus? And are they beneficial or harmful to your searches?
The origins of "indexed keywords"
Journal article records in Scopus are supplied directly from publishers, and thus arrive with no indexing. Scopus then enriches these references whenever possible, using thesauri Elsevier either owns or licenses. The “indexed keywords” that display in references are added when Scopus finds an exact item match with a reference from Embase or MEDLINE. For example, an article indexed in Embase will be enriched with most (but not all) Emtree terms; an article indexed in MEDLINE will have most (but not all) MeSH terms applied. References indexed in both Embase and MEDLINE will have terms from both thesauri. Some common examples of missing indexing include Emtree device terms and MeSH subheadings, neither of which will be found in Scopus indexed keywords.
How is the indexing different in Scopus, MEDLINE, and Embase?
PMID 38166804 is an illustrative example.
Scopus's MeSH for the same article are: Body Mass Index; Counseling; Female; Humans; Iran; Obesity; Pregnancy; Smartphone. What's different? Subheadings are not part of the Scopus record enrichment, nor are indicators of major topics.
The same article is also in Embase. The Embase record lists the following Emtree terms, with bold indicating "major focus": Device terms: mobile application; smartphone ; Other terms: adult; article; awareness; body mass; controlled study; counseling; data analysis; fast food; female; food intake; health care quality; health center; health education; human; major clinical study; prevalence; randomized controlled trial; sedentary lifestyle
Scopus's Emtree terms are: adult; Article; awareness; body mass; controlled study; counseling; data analysis; fast food; female; food intake; health care quality; health center; health education; human; major clinical study; prevalence; randomized controlled trial; sedentary lifestyle; body mass; counseling; Iran; obesity; pregnancy. What's different? Device terms are not part of the Scopus record enrichment, nor are indicators of major focus.
Do you want to search indexed keywords?
Since institutions who don't have MEDLINE access on a subscription interface can still use PubMed, whether or not to search indexed keywords is more likely to be determined based on Embase access.
For those without access to Embase, it may be beneficial to include indexed keywords in your search. While you cannot search the Emtree thesaurus directly, indexed keywords do allow you to take some advantage of the Emtree indexing. Unfortunately, it's not possible to exclude indexed keywords by thesaurus (e.g., to include Emtree terms, imperfect as they are, but exclude MeSH).
For those with access to Embase, it makes sense to exclude indexed keywords. You'll already be able to take full advantage of the Emtree thesaurus and perform searches with appropriate vocabulary and syntax directly in Embase. In addition, inconsistent or incomplete index terms originating from the enriching process may introduce a lot of unnecessary noise when searching a database the size of Scopus.
How do you include or exclude indexed keywords?
Scopus offers three different field codes (see the Scopus Support Hub for a full list of available field codes) for searching keywords:
- AUTHKEY searches keywords assigned by authors, which are part of the original publisher records.
- INDEXTERMS searches controlled vocabulary terms added to Scopus during the enrichment process described above. Searches of INDEXTERMS also “take into account synonyms, various spellings, and plurals.” As with other searches in Scopus, using “quotation marks” does a loose phrase search; to work around whatever automated actions Scopus normally takes with INDEXTERMS searches, use {curly brackets} around exact phrases, bearing in mind that truncation cannot be used within curly brackets.
- KEY is a composite field that searches the fields AUTHKEY, INDEXTERMS, TRADENAME, and CHEMNAME. The default search in Scopus, TITLE-ABS-KEY, includes this field code.
To include indexed keywords, simply use the default KEY field, either on its own or in a TITLE-ABS-KEY search.
To exclude indexed keywords, use the AUTHKEY field rather than KEY. There is no combined field search of this type, so researchers can use the Advanced Document Search option to search TITLE-ABS() OR AUTHKEY() to replace TITLE-ABS-KEY()
The Scopus search history below shows the significant differences in search results when including or excluding indexed keywords. For accessibility and ease of replicating the search, the full history is provided in both text and image.
Search History
| Line number | Search string | Number of results |
|---|---|---|
| 5 | TITLE-ABS-KEY ( ( smartphone* OR "mobile application*" ) AND "body mass" ) | 1430 |
| 4 | ( TITLE-ABS ( smartphone* OR "mobile application*" ) OR AUTHKEY ( smartphone* OR "mobile application*" ) ) AND ( TITLE-ABS ( "body mass" ) OR AUTHKEY ( "body mass" ) ) | 598 |
| 3 | KEY ( ( smartphone* OR "mobile application*" ) AND "body mass" ) | 856 |
| 2 | INDEXTERMS ( ( smartphone* OR "mobile application*" ) AND "body mass" ) | 753 |
| 1 | AUTHKEY ( ( smartphone* OR "mobile application*" ) AND "body mass" ) | 15 |
For additional information on Scopus content and how indexing appears in its records, consult the current Scopus Content Coverage Guide.
Many thanks to Zahra Premji, University of Victoria Libraries, and Krizia Tuand, Learning Centre Désiré Collen, KU Leuven Libraries – 2Bergen, Belgium and co-secretary of the EAHIL special interest group for evidence-based information, for their insights on this topic.
Hilary, this is another great post. I just discovered this NOT-based CADTH search filter for SCOPUS that removes citations derived from the MEDLINE/PubMed and Embase databases. https://searchfilters.cadth.ca/link/97
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