Health Sciences Descriptors

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This article presents the trilingual and structured DeCS vocabulary. DeCS is the Spanish and Portuguese acronym for Descriptores en Ciencias de la Salud, or Health Sciences Descriptors. DeCS was created by BIREME for use in indexing articles from scientific journals, books, congress proceedings, technical reports, and other types of materials, as well as for searching and retrieving subjects from scientific literature in LILACS, MEDLINE and other data bases.

DeCS is part of the LILACS methodology and together with LIS - Health Information Locator - is an integrating component of the Virtual Health Library.

DeCS follows the tradition of the classification systems and their respective subject heading lists which have been transformed into specialized vocabularies without, however, changing the structures of the classification systems from which they originated. Its tree structure is well-grounded in the division of knowledge in decimal classes and subclasses respecting their conceptual and semantic relationships, and its terms are presented in a hybrid structure of pre- and post-coordination.


DeCS (Health Sciences Descriptors) is a controlled and structured vocabulary in four languages in the area of health.


The DeCS vocabulary was created in the late 1970s when BIREME requested authorization from the U.S. National Library of Medicine (NLM), responsible for MeSH (Medical Subject Headings) for its translation and adaptation into Spanish and Portuguese.


Be the standard language to facilitate access to scientific information of the Latin American and Caribbean Region (LA&C).


DeCS organizes the field of knowledge of health sciences and is used in indexing and retrieval of information sources of the Virtual Health Library (VHL). DeCS, maintained by BIREME, is an integrating component of the VHL and also functions as a conceptual map for navigation support for themes in the VHL information sources in Portuguese, Spanish and English.

DeCS includes the MeSH vocabulary. This terminological compatibility and commitment to its annual updating and corresponding translation into Portuguese and Spanish allowed the effective cooperation with the project UMLS (Unified Medical Language System, NLM) since 1997. The UMLS project aims to develop a language of health information retrieval with features of a world-wide expert system.

This set of terminology represents the health sciences domain in the information sources of the NLM and VHL; it is an essential resource for the development and consolidation of tools for advanced search and navigation in information sources of the VHL, SciELO and associated networks as for example, in searching by lexical proximity by trigrams.

2020 Edition

As of April 2020 DeCS has a total of 34.118 concepts and 662 thousand terms: 448.905 terms in English, Portuguese and Spanish Latin America, 85.498 terms in Spanish from Spain and 127.406 in French. These terms are organized in 16 categories common to MeSH and DeCS and four exclusively DeCS categories, which are: Science and Health, Homeopathy, Public Health and Health Surveillance. Read more

Previous Editions

Link Concepts Terms
DeCS 2019 33.966 520.659
DeCS 2018 33.479 423.293
DeCS 2017 33.053 408.473
DeCS 2016 32.482 219.215
DeCS 2015 32.160 215.435
DeCS 2014 31.865 209.222
DeCS 2013 31.580 205.487
DeCS 2012 31.322 203.174
DeCS 2011 30.899 199.696
DeCS 2010 30.369 191.775
DeCS 2009 29.980 186.416
DeCS 2008 29.573 182.247
DeCS 2007 29.167 177.649
DeCS 2006 28.691 172.963
DeCS 2005 27.683 164.501
DeCS 2004 26.850 159.958
DeCS 2003 26.261 154.927
DeCS 2002 24.966 141.806
DeCS 2001 24.299 135.402
DeCS 2000 24.027 134.046
DeCS 1999 22.766
Graph of annual growth of the number of MeSH/DeCS terms from 1960 to 2020
Graph of annual growth of the number of MeSH/DeCS concepts from 1960 to 2020


Management System

The BIREME team of DeCS/MeSH experts, together with experts from several other MeSH translation centers, participated between 2014 and 2019 in the translation of MeSH through the NLM online system called MeSH Translation Maintenance System (MTMS). As of version 2020, BIREME started using a new version of its own DeCS management and translation system, compatible with the MeSH DTD file format and with other BIREME processes, such as being multi-user, supporting multiple languages and multiple thesauri.

Search System

The DeCS Search System is an open access trilingual web-based application for searching the DeCS vocabulary and for indexing and retrieving technical and scientific health information indexed with this vocabulary.

It permits searches in English, Spanish and Portuguese, and indexing by colaborating centers when included in BIREME's LILDBI_Web application. It also links with UMLS vocabularies, the VHL information sources, and web services.

English, Spanish and Portuguese interfaces.

How to search in the English, in the Spanish, and in Portuguese interfaces. The following presentations include examples of how to use this system, some of them created after the publication of the above documents. (Presentation in English, Spanish and Portuguese)

User Support System

The DeCS User Support System is a web-based software for user contact with the DeCS team.

Users are informed of BIREME's address, phone and fax numbers and, if desired, may fill in four fields: name, e-mail, subject and message body. After clicking the "send" button, an automatic message is shown saying the message was sent and the user may click on the "back" button to return to the DeCS homepage.

Form in English, Spanish and in Portuguese.



Projects Presented at Conferences


  • MeSH Suggestion page - For English suggestions fitting in MeSH categories, the link on the left will remit you to NLM's MeSH suggestion page.
  • DeCS suggestion page - For Spanish or Portuguese suggestions fitting in MeSH categories and suggestions in any of DeCS's three languages fitting in the DeCS-exclusive categories, please fill out form at the link on the left and forward it attached to an e-mail to bir.decs [at] or fill out this form.

Update Guide


DeCS web pages


DeCS Searches

  • DeCS Search
  • Direct Search
  • Search via trigrams
  • Alphanumeric Ruler
  • Descriptor Types:
    • Checktags: Type _P in the alphabetical index of the Search System to see the checktags (or limits).
    • Publication Types: Type a _T in the alphabetical index of the Search System to see the publication types or access the tree index and navigate in the V category, Publication Characteristics, which contains all the publication types.
    • Qualifiers: qualifiers are normally searched in the alphabetical index or in the "Search by Word" field and selecting the Exact Descriptor option button, and typing the entire term preceded by a slash /, because they start with a slash (eg /blood) in DeCS.
      • For searching the two letter abbreviation of qualifiers, type Q = <the two letter abbreviation> in the "Search by Word" field and selecting the Exact Descriptor option button.
      • In order to see all qualifiers in alphabetical order, see the alphabetical ruler. Searching the qualifier tree structure is done here.
  • ID DeCS: In order to search for DeCS ID's, type MFN=<ID DeCS> in the "Search By word" field and select the "Exact Descriptor" option.
  • ID MeSH: In order to search for MeSH ID's, type UID=<ID MeSH> in the "Search By word" field and select the "Exact Descriptor" option.

DeCS Web Services


Format conversion

Procedures for MeSH Format Conversions

The NLM MeSH vocabulary exists in four formats: MARC, ASCII (or Elhill), XML, and RDF. Currently, the DeCS team downloads MeSH in ASCII and XML formats. The ASCII version is then converted to ISIS, for consistency checks. Beginning with the 2019 DeCS version, BIREME imports data directly from this XML for automatic updating DeCS with MeSH's fields. After DeCS is updated in three languages, subset extractions of DeCS or the entire DeCS conversion to other formats is then made possible.

ASCII (or Elhill) to ISIS
ISIS to txt
Txt to Excel or colon separated values (.csv)

Insertion of translations into the vocabulary

Translations are inserted for new concepts or for concepts that perhaps lacked a scope note or indexing annotation.

Insertion of translation using the maintenance system

The insertion of translations using the maintenance system is done for English, for the Latin American Spanish variant, and for Portuguese contents.

Insertion of translations not using the maintenance system

The insertion of translations from outside of the maintenance system occurs for adding large amounts of new concepts, new hierarchical branches or categories, as well as fields related to translations and updates of the variant of Spanish from Spain, not foreseen in the current maintenance system.

Insertion of vocabulary changes

Changes are made using the maintenance system or not, just as it happens for translations of new concepts, terms and notes, when they are modified for some reason. Updates can be changes in the spelling of a word when its concept has changed or ceased to exist, switching the preferred term with one of its non-preferred terms, changes in the grammar rules of the language.

Consistency checks

Within the maintenance system

  • check when moving a term from an active field to a historical field

When a term is eliminated from a preferred term field or from an alternative term field, the system moves it automatically to the historical field. The historical field contains the following information: date it was removed from the vocabulary, the term, and which field it used to be in.

  • terminological duplication check

When a term is placed in a preferred term field or in an alternative term field, the system checks for its existence in these fields and in the historical term field, for that language. If it already exists as a preferred or alternative term, the system alerts the user of this fact by informing the other ID. The user than needs to correct this duplication before he can complete the action.

  • check when moving a term from a historical field to an active field

When a term is placed in a preferred term field or in an alternative term field, the system checks for its existence in these fields and in the historical term field, for that language. If it already exists as a historical term, the moment the user saves the change, the system eliminates the term from the historical field and informs the user of this change.

  • subfield use check

Checks for the existence of the n subfield for notes fields, and the d subfield for the MeSH-suggested term field.

From outside of the maintenance system

duplication checks

Duplications are checked for terms and hierarchical codes. The DeCS vocabulary has neither terminological duplication in any of the three languages nor duplication between the languages. Hierarchical codes are also unique for each descriptor record.

check for excess or lack of MeSH terms

After the replaced MeSH descriptors are updated in DeCS and the new MeSH records are added at the end of the DeCS file, both files are compared. Three lists are produced in this check:

  • Terms that exist in MeSH but are absent in DeCS (these are either terms that were not correctly updated or are new synonyms.)
  • Terms that exist in DeCS but are absent in MeSH (these are either terms that were not correctly updated or are synonyms that are to be excluded from DeCS)
  • Terms that exist in DeCS and MeSH, but that are in diferent IDs (these are synonyms that moved from one ID to another)

check for strange characters

See Related Descriptor check

Changes in or elimination of a descriptor affects the descriptors that appear in the "See related" field. For this reason, the descriptors in this field are checked for their existence as descriptors and a list is produced for correction.

Suggested MeSH Descriptor check

The same reasoning above applies to this field, which exists in non-MeSH concepts, i.e., from the HP, SH, SP and VS categories.

Other checks

The following fields are also checked for its compatibility with MeSH: The MeSH Unique Identifier, Pre-explosion, Tree node allowed, Entry combination and New MeSH synonyms subfield.

See also