This section last updated: 2020-06-26 (3 years ago)
Each coding system is designed for a specific purpose. The following is a brief discussion of a coding systems.
LOINC codes are useful for both ordering and resulting of test results. LOINC has been widely recognized and recommended for transmitting laboratory and clinical observations in HL7 messages. A short (non-exhaustive) list of recommendations include:
CPT codes may be used for ordering and billing purposes. Often, CPT codes are not as specific as LOINC codes. For example, one CPT code may have multiple LOINC codes associated with it. Many lab tests will not have specified CPT codes associated with the "parts" of a lab test. For example, % basos, though there is a CPT code tor order a differential (Blood count; automated differential WBC count), but there is not an individual code to represent the result of percent basophils in a differential.
The National Library of Medicine has sponsored a LOINC to CPT mapping. The first draft mappings are available through the UMLS website and NLM is happy to receive comments about the usefulness of this mapping.
SNOMED is a large, comprehensive computerized clinical terminology covering clinical data for diseases, clinical findings, and procedures. In HL7 ORU messages, LOINC provides codes for the question (OBR-4, OBX-3) while SNOMED provides codes for the answers (OBX-5).
Yes and no. The National Library of Medicine sponsored a LOINC to CPT mapping that was performed by Intermountain Health Care and reviewed by Regenstrief and the AMA in 2005-06. That effort mapped terms from LOINC version 2.15 to the 2005 version of CPT and covered many, but not all, of the common laboratory tests. The original intent was to periodically update and expand the LOINC to CPT mappings, but due to funding and other resource issues, the project did not continue.
The basic use-case for the original mapping effort was that LOINC codes would be used for ordering/reporting tests and observations, and the associated CPT codes would be used for billing; thus, this was a unidirectional map from LOINC codes for orders/results to CPT billing codes. The mapping table and more information about the process and mapping assumptions that were made are available through NLM's UMLS website.
The International Classification of Diseases (ICD) is primarily a code system for recording diagnoses whereas LOINC is a code system for identifying test observations. There are a few test codes in ICD-10 Clinical Modification (ICD-10-CM) for use in hospital billing only.