OHDSI Home | Forums | Wiki | Github

Why are there multiple entries for the same concept?

I downloaded some concept list from ATHENA and wanted to upload it into our own database. It seems it would be easier when we join tables to see what we are querying.

However, the more I look at those concepts I am confused. Why are there multiple entries for the same concept as below?

I cannot find the synonym in the synonym tables either. And not sure what these are different to each other?

So what are these? Thanks

Yeah, that looks confusing.
But that’s how NDC encodes this, look here for example, all the codes are listed there.

The good thing that all of these NDC Oxygen concepts are mapped to the same RxNorm concept oxygen 99 % Gas for Inhalation, so this problem doesn’t bother you when you do the research using an OMOPed data.