^A47
ADT^A47 — Change Patient Identifier List
Sent when a patient's identifier — most commonly their Medical Record Number (MRN) — is changed. The PID segment contains the new identifier; the MRG segment contains the old identifier that is being replaced. All downstream systems must update their records to use the new identifier.
When Is This Sent?
When a patient's MRN or other identifier is changed in the source system — for example, when migrating from one MRN format to another, correcting a data entry error in the MRN, or assigning a new enterprise identifier.
Real-World Usage
A47 is critical during MRN migrations and system replacements. Every downstream system that stores patient identifiers — PACS, RIS, lab, pharmacy, billing — must receive and act on A47 messages, or they will continue using stale identifiers that no longer match the master source. A missed A47 in one system creates a silent identity mismatch that may not surface until the patient's next encounter.
Message Structure
Segment names link to their field-level reference pages.
Example Message
Realistic example with fake patient data. Paste into the HL7 Message Viewer to explore interactively.
1MSH||^~\&|EPIC|HOSPITAL_A|MIRTH_PROD|PACS|20260312130000||ADT^A47^ADT_A47|MSG00115|P|2.5.1 2EVN||A47|20260312130000 3PID||1||NEW_123456^^^HOSP_A^MR||Smith^John^M^^Mr.||19850315|M 4MRG||OLD_123456^^^HOSP_A^MR
Troubleshooting Scenarios
Patient not found in downstream system after MRN change
Cause
Downstream system did not receive or process the A47 and still has the old MRN. Subsequent messages with the new MRN fail to match the patient.
Fix
Re-send the A47 to the downstream system and confirm it was processed. Verify the old MRN in MRG.1 and the new MRN in PID.3 are both correctly formatted. After processing, test patient lookup by new MRN in the downstream system.
Historical studies in PACS not linked to new MRN
Cause
PACS updated the patient record identifier but did not retroactively update the patient demographic data stored on existing DICOM studies.
Fix
Confirm with the PACS vendor whether A47 triggers a retroactive DICOM study re-tag or only updates the PACS database record. For DICOM compliance, the PatientID (0010,0020) on existing studies may need to be updated via a PACS administration or DICOM retag operation.
Common Confusions
ADT^A47 (Change Patient Identifier) vs ADT^A40 (Merge Patient). A47 changes an identifier for a single patient — the patient record is the same, only the ID changes. A40 merges two separate patient records into one. If a patient has two MRNs because of duplicate registration, use A40 to merge. If a patient has one MRN that needs to be changed or corrected, use A47.
Related Message Types
Segment Reference
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