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Unified Medical Language System (UMLS)

CDT (Current Dental Terminology) - Metathesaurus Representation

This page lists UMLS Metathesaurus data elements and traces them back to the specific source data that populates them.

Skip to: Atoms, Attributes, Definitions, Relationships, Mappings


Summary of Changes

There were no changes to the original file format or to Metathesaurus source processing.


  • In the printed CDT book, some codes appear out of order. The order information is not available in electronic form, therefore the UMLS hierarchy varies slightly from the hierarchy in the printed book.
  • A value of "None" in the original data is treated the same as a blank or null value.
  • CDT in the Metathesaurus is extracted from a file provided by the American Dental Association (ADA). The Metathesaurus also includes the HCPCS version of CDT, which has RSAB = "HCDT." The CDT hierarchy is created from the data file provided by the ADA, while the HCDT hierarchy is created during Metathesaurus production using analysis of the HCPCS printed manual.

Source Provided Files:

File Name Description
b_CDT2018ASCII_2017June26.txt Documentation and tab-delimited data
a_CORRECTED_Read Me_CDT 2018.pdf Documentation


Identifiers are assigned as follows:
  • CODE:
    • TTY = PT, TTY=OP: the value of the Code field from tab-delimited data file
    • TTY = HT: A range, e.g. "D4000-D4999," indicating the high and low code values encompassed by the HT; this value is computed during Metathesaurus source processing.
  • SAUI: Not applicable
  • SCUI: Same as CODE
  • SDUI: Not applicable

Atoms (MRCONSO):

Term Type Origin
A range, e.g. "D4000-D4999." This value is computed, based on the low and high code values encompassed by the HT.

STR: The value of the "Category," "Subcategory," or "Subsubcategory" field.

SCUI: Same as CODE

Suppress = 'N'

One atom with TTY = HT is created for all unique values of "Category," "Subcategory" and "Subsubcategory."
OP CODE: The value of the Code field from tab-delimited data file.

STR: The value of the "Nomenclature" field in the tab-delimited file.

SCUI: Same as CODE

Suppress = 'O'

TTY = OP is assigned where the Class1 value = 99 (The entire CDT Code entry is no longer valid, i.e. it was deleted in this version). Note: deleted codes are only retained for one version. Codes deleted in previous CDT versions are no longer present in the ADA data.
PT CODE: The value of the Code field form tab-delimited data file

STR: The value of the "Nomenclature" field in the tab-delimited file.

SCUI: Same as CODE

Suppress = 'N'

TTY = PT is assigned where the the Class1 value is not 99.

Attributes (MRSAT):

ATN Origin Notes
CHANGE_CLASS The value of the "Class" field in the tab-delmited file. Identifies the type of change made to this version of the Code (i.e., changes from the prior version), with the following meanings:
  • 30 = No change to existing code, nomenclature or descriptor
  • 31 = New procedure code and nomenclature, and descriptor, if present
  • 35 = Revision in the nomenclature or descriptor (or both), or to indicate a revision to an entire subcategory."
  • 99 = Entire CDT Code entry is no longer valid (i.e., deleted) in this version.
SOS The value of the Descriptor, CatDescriptor, SubcatDescriptor or SubsubcatDescriptor Previously represented as DEFINITION

Definitions (MRDEF):

There are no definitions in CDT. Data that was previously represented as definitions is now represented as ATN = SOS.

Relationships (MRREL); Hierarchy (MRHIER)

REL RELAInverse RELA Origin
(no RELA) Hierarchy, created based on the Category, Subcategory and Subsubcategory fields. PTs are leaf nodes.
SIB (no RELA) Relationships between codes with the same parents.

Mappings (MRMAP):

No mappings are supplied for CDT.