I have a couple of suggestions for your issue X1, X2, X3, etc modifiers, @Richard_Starr. Is this data from Illinois or Wisconsin or Michigan? Modifiers X1-X9 are local modifiers used to indicate equipment was transported somewhere. I found some information about it here. Since these modifiers are indicated at the state level, it doesn’t surprise me that they are not in the OHDSI vocabularies. I know that there are very specific Medicaid modifiers used in California too. I’m not sure how to reconcile this into the vocabularies. But I’ll leave all the heavy lifting to @Christian_Reich
I also like your suggestion of using the fact_relationship table, but I am concerned that it would not pick up the unmapped modifiers. I actually really like your first suggestion of just putting the comma-separated modifiers in the qualifier_source_value and set the modifier_concept_id = 0. Smart!