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Unified Medical Language System® (UMLS®)

ICD-9-CM Procedure Codes to SNOMED CT Map

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ICD-9-CM Procedure Codes to SNOMED CT Map File

Derived from ICD-9-CM version

Derived from SNOMED CT version



July 2012 International Release

SNOMED CT (Systematized Nomenclature of Medicine - Clinical Terms) is considered to be the most comprehensive, multilingual clinical healthcare terminology in the world. It is designed for use in clinical documentation in the Electronic Health Record (EHR).  SNOMED CT is one of the required standards for procedures in the 2014 Certification Criteria for EHR products that may be used to qualify for meaningful use incentives.  This map is designed to support a transition from the use of legacy ICD-9-CM procedure codes to SNOMED CT.

The most useful mappings are the one-to-one maps, in which a single SNOMED CT concept can be used to represent the full meaning of an ICD-9-CM code. This allows the automatic translation of ICD-9-CM codes into SNOMED CT codes without loss of meaning. In the creation of the map, we tried to identify as many one-to-one maps as possible. However, due to the differences between the two coding systems, this is not possible for some ICD-9-CM codes. The Map is published in two separate files, one containing the one-to-one (exact) maps, and the other the one-to-many (partial) maps. In the partial maps, the target SNOMED CT concept can be broader or narrower than the meaning of the ICD-9-CM code.

Mapping Methodology
In-patient claims data for 2011 were obtained from the Centers for Medicare & Medicaid Services (CMS). Using the UMLS, we identified synonymy relations between ICD-9-CM terms (both the main rubric and inclusion entries) and SNOMED CT concepts, which formed the basis of the map. One-to-one synonymy between the ICD-9-CM rubric and a SNOMED CT concept was accepted as valid one-to-one map and not manually reviewed. One-to-many maps were manually reviewed for validity and converted to one-to-one maps if possible. Frequently-used ICD-9-CM codes which fell within the 95th percentile of usage and did not have any UMLS maps were manually reviewed for possible mappings. All target SNOMED CT codes belong to the Procedure hierarchy.

Summary Statistics

Map Type

ICD-9-CM codes

% of usage covered by the ICD-9-CM codes

1-1 Maps

1,709 (46.9%)


1-M Maps

490 (13.4%)


No Map

1,446 (39.7%)



3,645 (100%)


Versions of Terminologies and Knowledge Sources

  • ICD-9-CM – the CMS data was based on the 2011 version. The 2013 version was used in the Map. One code from the CMS data had become obsolete, but was kept in the map because obsolete codes might be present in legacy data and so their maps would still be useful
  • SNOMED CT – July 2012 release
  • UMLS – 2012AB release

Data Format
The Map is published as two tab-delimited value files with the same file structure. The file ICD9CMV3_SNOMED_MAP_1TO1.txt contains the ICD-9-CM codes with one-to-one maps, and the file ICD9CMV3_SNOMED_MAP_1TOM.txt contains the ICD-9-CM codes with one-to-many maps. For completeness, the second file also contains the ICD-9-CM codes that do not have a map. The fields are:

  • ICD_CODE – ICD-9-CM code
  • ICD_NAME – ICD-9-CM description
  • IS_CURRENT_ICD – whether ICD-9-CM code is still current in the 2013 version
  • IP_USAGE - % of total code usage in in-patient claims data
  • SNOMED_CID – SNOMED CT concept identifier, the target of the map (null for ICD-9-CM codes without a map)
  • SNOMED_FSN – SNOMED CT fully-specified name (null for ICD-9-CM codes without a map)

License Requirements
In accordance with NLM’s mapping assumptions, the Map can be used by users who are licensed to use both SNOMED CT and ICD-9-CM. SNOMED CT is owned by the International Health Terminology Standards Development Organisation (IHTSDO), of which NLM is the US Member. Use of SNOMED CT is free in IHTSDO Member countries including the United States, in low income countries, and for approved research projects in any country, but is subject to the IHTSDO Affiliate license provisions (incorporated in the License Agreement for Use of the UMLS® Metathesaurus® as Appendix 2). The use of ICD-9-CM is free.

Comments and questions
We welcome any questions, comments or suggestions that would improve the quality, accuracy and usability of the Map. Please send feedback via e-mail to Dr. Kin Wah Fung, Lister Hill National Center for Biomedical Communications, National Library of Medicine through NLM’s Customer Service with the subject line “ICD-9-CM Procedure Codes to SNOMED CT Map”.