ADT/ACK - Merge Patient - Patient Identifier List (Event A40)

An A40 event is used to signal a merge of records for a patient that was incorrectly filed under two different identifiers. The "incorrect source identifier" identified in the MRG segment (MRG-1 - Prior Patient Identifier List) is to be merged with the required "correct target identifier" of the same "identifier type code" component identified in the PID segment (PID-3 - Patient Identifier List). The "incorrect source identifier" 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.