HL7 ADT_A50 Change Visit Number

The visit is the same visit, but the visit number was wrong.
HL7 message structure ADT_A50 groups and segments from HL7 v2.5.1 Hide structure

These are the generated groups and segments for the version selected at the top of the page. The article explains the workflow, and this panel follows the chosen HL7 version.

Message Structure

SegmentNameRequiredRepeatable
MSH
 Message Header Yes No
SFT
 Software Segment No Yes
EVN
 Event Type Yes No
PID
 Patient Identification Yes No
PD1
 Patient Additional Demographic No No
MRG
 Merge Patient Information Yes No
PV1
 Patient Visit Yes No

ADT_A50 changes an incorrectly assigned visit number. It is not a move to another patient, and it is not a merge. The patient and account context should match; the correction is at the visit identifier level.

This event matters because visit number is often the practical join key for orders, results, documents, charges, images, and patient movements. A small visit-number typo can scatter data across systems.

A small A50 example

MSH|^~\&|ADT|CITYHOSP|EHR|CITYHOSP|20260715161000||ADT^A50^ADT_A50|ADT500001|P|2.5.1 EVN|A50|20260715160900 PID|1||123456^^^CITYHOSP^MR|||||||||||||||ACC0002^^^CITYHOSP^AN MRG|123456^^^CITYHOSP^MR||ACC0002^^^CITYHOSP^AN||VNOLD001^^^CITYHOSP^VN PV1|1|I|WARD1^101^1^CITYHOSP^^BED||||12345^Ng^Grace|||||||||||VN000345^^^CITYHOSP^VN

What systems do with it

The sender is typically the PAS/EHR or registration correction workflow. Receivers update correlation tables and visit-scoped records from the prior visit number in MRG to the corrected visit number in PV1.

How to read the structure

The structure is MSH, EVN, PID, optional PD1, required MRG, and required PV1. MRG-5 carries the prior visit number. PV1-19 carries the corrected visit number.

Implementation traps

Do not create a second visit. A50 is a change of identifier on the same visit. Also be careful with partial identifiers: if assigning authority or identifier type is missing, a receiver may update the wrong visit in a multi-facility environment.

Reference notes

The HL7 v2+ ADT_A50 page describes changing an incorrectly assigned visit number, with the incorrect value in MRG-5 and the correct target value in PV1-19.