A merge has been done at the external identifier level. That is, two PID-2-patient ID (external ID) identifiers have been merged into one.
An A39 event is used to signal a merge of records, for a person that was incorrectly filed under two different external IDs. The "incorrect source external ID" identified in the MRG segment (MRG-4-prior patient ID-external) is to be merged with the required "correct target external ID" identified in the PID segment (PID-2-patient ID (external ID)). The "incorrect source external 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.
Since this event is a merge at the PID-2-patient ID (external ID) identifier level, PID-3-patient ID (internal ID) and MRG-1-prior patient ID - internal ID are not required.
The external IDs involved in identifying the persons may or may not be patients, who may or may not have accounts, which may or may not have visits. An A39, merge person information An A39 (merge person - external ID) event is intended for merging person records without merging other subordinate identifiers. Any other subordinate identifiers that were previously associated with the "incorrect source external ID" are now associated with the "correct target external ID". Specification of these other subordinate identifiers is not required to be provided.
This event and the message syntax do, however, allow for the specification of "new subordinate identifiers" (in addition to the PID-2-patient ID (external ID) identifier). For those environments that may require changes to these other subordinate identifiers because of this, merge person event A39, an A39 (merge person - external ID), it is required that the old and new identifiers be a "tightly coupled" pair.
See section 3.5.2, "Merging patient/person information," for a discussion of issues related to the implementation of merge messages.
All data associated with the "correct target external ID" are treated as updated information.
ADT ADT Message Chapter
MSH Message Header 2
EVN Event Type 3
{ PID Patient Identification 3
[ PD1 ] Additional Demographics 3
MRG Merge Information 3
[ PV1] Patient Visit 3
}
ACK General Acknowledgment Chapter
MSH Message Header 2
MSA Message Acknowledgment 2
[ ERR ] Error 2