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Table of Contents: 2013 MARCH–APRIL No. 391

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MeSH Unique Identifiers: Length Expanding to Ten Characters

Hui C, Schulman J. MeSH Unique Identifiers: Length Expanding to Ten Characters. NLM Tech Bull. 2013 Mar-Apr;(391):e1.

2013 March 06 [posted]
2013 April 24 [Editor's note added]
2014 May 05 [Editor's note added]

[Editor’s Note: The length of the unique identifiers used for Descriptors, Qualifiers, and Supplementary Concept Records in the MeSH Vocabulary will expand to 10 characters on or about May 19, 2014.]

Due to the ever increasing number of concepts and terms in MeSH, it is necessary to increase the number of unique identifiers (UI) available for the MeSH vocabulary. Thus, the length of the unique identifier elements used in Descriptor, Qualifier, and Supplementary Concept Records will expand to 10 characters. Most UIs are currently 7 characters in length; one (the Concept UI) is currently 8 characters. The change to 10 characters will begin for unique identifiers created on and after April 15, 2013. [Editor's note added April 24, 2013: The implementation of the 10-character unique identifiers has been postponed from April 15, 2013 to November 2013.]

The format of existing unique identifiers will not be changed. For example: If D009710 is the last descriptor UI on April 15, then the next descriptor UI would be D000009711.


Record Type UI Existing Unique Identifier Format Future Unique Identifier Format
Descriptor D064418 Dnnnnnnnnn
Qualifier Q000941 Qnnnnnnnnn
SCR C578561 Cnnnnnnnnn
Concept or Term UI    
Concept M0581777 Mnnnnnnnnn
Term T837922 Tnnnnnnnnn

For users of the MeSH XML data, the XML elements affected are:

<ConceptUI> for M number
<DescriptorUI> for D number
<QualifierUI> for Q number
<SupplementalRecordUI> for C (or SCR) number
<TermUI> for T number

By Chris Hui and Jacque-Lynne Schulman
MeSH Section

NLM Technical Bulletin National Library of Medicine National Institutes of Health