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Question about Observation.unit_source_value field


I am working on the ETL logic of the codes, and come to a question about storing the unit of the numeric value. For example, imagine if I want to store a result, something like “3mm” in the Observation table, I thought my ETL logic would put:

  • “3” → “value_as_number”
  • “8588” → “unit_concept_id”
  • “mm” → “unit_source_value”
  • “3mm” → “value_source_value”.

Is this correct?

I would like to check this because when I read the documentation (OMOP CDM v5.4), there is a note next to the “unit_source_value” field, which says:

“This code is mapped to a Standard Condition Concept in the Standardized Vocabularies and the original code is stored here for reference.”

I am not sure how “unit_source_value” is related to the Condition concept … I wonder what I may be missing in my understanding.

Any feedback is welcome. Thank you!!