The figure above shows the two standard concepts of red blood cell distribution width in OMOP
Red blood cell distribution width [ratio]
Red blood cell distribution width [entity volume]
The corresponding units are
The question I want to ask is whether there is a definition of the relationship between the corresponding units of the laboratory inspection items in omop. If not, the unit can only be judged by humans and not reflected in the terminology?
The LOINC source code for laboratory inspection items only maps to a standard concept_id for the Measurement and not to a unit_concept_id. In the US EHR data I have seen, the unit information for a laboratory test is a separate field from the LOINC code and is mapped to a unit_concept_id.