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National Library of Medicine Technical BulletinNational Library of Medicine Technical Bulletin

Table of Contents: 2018 MAY–JUNE No. 422

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UMLS 2018AA Release Available

Wilder V. UMLS 2018AA Release Available. NLM Tech Bull. 2018 May-Jun;(422):e1.

2018 May 08 [posted]

The 2018AA release of the Unified Medical Language System (UMLS) Knowledge Sources is available for download as of May 7, 2018.

The 2018AA Metathesaurus contains approximately 3.67 million concepts and 14 million unique concept names from 203 source vocabularies.

One new source:

  • MED-RT (Medication Reference Terminology)

One new NCI sub-source:

  • NCI_CTRP-SDC (NCI Clinical Trials Reporting Program)

NDF-RT update:

  • This release includes the final update of NDF-RT. Note that MED-RT is its successor.

Sixty-three English sources and 40 translation sources were updated. These include MeSH, MedDRA, RxNorm, and SNOMED CT® (English and Spanish). A complete list is available in the Updated Sources section of the Release Documentation. For more detailed information on changes in this version of the Metathesaurus, see the Updated Sources (Expanded) section. Additional release statistics may be found in the Statistics section.

SPECIALIST Lexicon and Lexical Tools

  • The release includes the updated SPECIALIST Lexicon (2018 Release).
  • The release includes the updated Lexical Tools (2018 Release) which integrate data from the SPECIALIST Lexicon, 2018 Release. The Lexical Tools include the Full and Lite versions of lvg.2018.
  • The Metathesaurus index files were processed using the updated lvg files.
  • The updated SPECIALIST Lexicon and Lexical Tools feature synonym enhancements that include changes to their file structure. See the SPECIALIST Lexicon and Lexical Tools Web sites for details about these file changes and other updates.


  • The full release requires 28.2 GB of disk space.

Reported bugs may be viewed on the Release Notes and Bugs Web page.

MetamorphoSys can generate custom load scripts for MySQL, Oracle, or Microsoft Access when creating a Metathesaurus subset or installing the Semantic Network. Instructions are available on the UMLS Load Scripts homepage.

Release Information
To access the UMLS Release files, you must have an active UMLS Metathesaurus License and a valid UTS account. You will be prompted for your UTS username and password when downloading the files. 

UMLS Learning Resources
2018AA Source Release Documentation Web pages are available.

Additional information regarding the UMLS is available on the UMLS homepage. New users are encouraged to take the UMLS Basics Tutorial and to explore the UMLS Quick Start Guide, and other training materials.

UMLS Terminology Services (UTS)
The UTS Metathesaurus Browser and the UTS SOAP API and REST API include the updated release.

In addition, the UTS SNOMED CT Browser now features the March 2018 US Edition of SNOMED CT.

By Victoria Wilder
MEDLARS Management Section

NLM Technical Bulletin National Library of Medicine National Institutes of Health