Here’s a buch of cases where the same concept can have different meaning.
For example it can be temporary HCPCS codes (like Q2042 and Q2041).
OHDSI has to have unique identifier (concept_id) for each concept,
in Athena you can see
Q2041 Axicabtagene ciloleucel
which is YESCARTA (current concept meaning).
but then you may notice that
It was Remapped to Injection, von willebrand factor complex (human), wilate, 1 i.u. vwf:rco
and this statement was true before 1-Jan-2019 (the date Q2041 become YESCARTA)
So, to represent Q2041 as YESCARTA in 2019
and Q2041 as von willebrand factor complex we need to make two entries in the CONCEPT table
|12345678 (new concept_id)||Q2041||YESCARTA||01-01-2019||31-12-2099|
|40664685 (old concept_id)||Q2041||von willebrand factor complex||01-01-1970||31-12-2018|
and respectively CONCEPT_RELATIONSHIP will have these relationships:
40664685 (old concept_id) Maps to von willebrand factor complex concept
12345678 (new concept_id) Maps to YESCARTA concept
Please let me know your thoughts.