ADT/ACK - Merge patient - internal ID

An A40 event is used to signal a merge of records for a patient that was incorrectly filed under two different internal IDs. The "incorrect source internal ID" identified in the MRG segment (MRG-1-prior patient ID (internal) is to be merged with the required "correct target internal ID" of the same "identifier type code" component identified in the PID segment (PID-3-patient ID (internal ID)). The "incorrect source internal ID" would then logically never be referenced in future transactions. It is noted that some systems may still physically keep this "incorrect identifier" for audit trail purposes or other reasons associated with database index implementation requirements.