LOINC is a coding system for lab tests, but also for surveys, tests and other clinical procedures or activities that create a result, usually for a diagnostic purpose.
All LOINC source information is obtained from the LOINC websites that is supported by the Regenstrief institute, except the mapping between LOINC and CPT4, which is provided by the NLM: Generic LOINC Concept
All LOINC Concepts are Standard Concepts, while Concepts of the Source LOINC Class, LOINC Hierarchy are Classification Concepts.
Concepts in the LOINC vocabulary are assigned Concept Class as following:
|LOINC||CLASSTYPE=1||Lab Test||The Universal Lab Order Codes Value Set contains the most frequent lab orders|
|CLASSTYPE=2||Clinical Observation||Anything that can be tested, measured, or observed about a patient without removing a specimen|
|CLASSTYPE=3||Claims Attachment||Information necessary to adjudicate claims for ambulance, rehabilitation, or emergency room services|
|CLASSTYPE=4||Survey||Set of questions on a survey or form|
|CLASS||LOINC Class||Similar to the Concept Classes of each LOINC Concept, but more detailed and hierarchical|
|LOINC Hierarchy||CODE||LOINC Hierarchy||Similar to LOINC Class, but separate hierarchical system|
|LOINC Answer||AnswerStringID||Answer||Observation result value as an answer to a LOINC Concept|
LOINC Concepts can have a Measurement or Observation Domain. This is assigned as following:
|LOINC||CLASSTYPE=1 or 2||Measurement|
|CLASSTYPE=3 or 4||Observation|
|LOINC Class||Manual||Observation or Measurement|
|LOINC Answer||Meas Value|
Relationships are defined within LOINC and between LOINC and CPT and LOINC and SNOMED:
These relationships are defined as “LOINC - SNOMED eq” between “LOINC Hierarchy” Concepts and SNOMED Concepts representing the entity that is measured. Note that only a small fraction (1% as of late 2015) are currently mapped. Also, note that some of the mappings seem to confuse the testing for drugs with the drugs themselves.
These relationships are defined as “LOINC - CPT4 eq” between LOINC Lab Test Concepts and SNOMED Concepts. Note that only a small franction (2% as of late 2015) are mapped.
All internal “Is a” and “Panel contains” relationships participate in the creation of the CONCEPT_ANCESTOR table, creating an internal hierarchy within LOINC not connected to the larger Measurement or Observation Domain space.