Hello @Mark,
@zhuk is correct. It is best to use dates to determine if a source code is from ICD9CM or ICD10CM.
As an AOU partner, you’re in the US and have ICD9CM and ICD10CM codes in your EHR source data. On October 1, 2015, the US switched from using and billing with ICD9CM codes to using ICD10CM codes. So, you can match all ICD codes < Oct. 1, 2015 to vocabulary_id = ‘ICD9CM’ and all codes >= Oct. 1, 2015 to vocabulary_id = ‘ICD10CM’.