Three common procedure code systems are supported in the Standard Vocabulary:
- The International Statistical Classification of Diseases and Related Health Problems, Clinical Modification, Volume 3 (ICD-9-Procedure) codes maintained by the National Center for Health Statistics (NCHS) – vocabulary_id 3.
- The American Medical Association produce the Current Procedural Terminology (CPT-4) – vocabulary_id 4.
- The Healthcare Common Procedure Coding System (HCPCS) Level II codes maintained by the Center for Medicare and Medicaid Services (CMS) – vocabulary_id 5.
All three are used for the OMOP Standard Vocabulary as low-level concept codes for procedures. These low-level codes are linked to SNOMED-CT “Procedure” concepts for classification purposes.