HL7 ADT_A60 Update Allergy Information

A focused ADT event for changing patient adverse reaction information.
HL7 message structure ADT_A60 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
PV1
 Patient Visit No No
PV2
 Patient Visit - Additional Information No No
IAM
 Patient Adverse Reaction Information No Yes

ADT_A60 is used when person or patient allergy/adverse reaction information changes. Unlike older ADT messages that often carry AL1 as a snapshot-style allergy segment, A60 uses IAM, which supports action-code and unique-identifier style updates for repeating allergy records.

This is a safety-sensitive message. Receivers should treat it as clinical risk information, not just another demographic decoration on the ADT feed.

A small A60 example

MSH|^~\&|EHR|CITYHOSP|PHARMACY|CITYHOSP|20260715170000||ADT^A60^ADT_A60|ADT600001|P|2.5.1 EVN|A60|20260715165900 PID|1||123456^^^CITYHOSP^MR||Smith^Jane^Anne^^Ms^^L||19800314|F PV1|1|I|WARD1^101^1^CITYHOSP^^BED||||12345^Ng^Grace|||||||||||VN000345^^^CITYHOSP^VN IAM|1|DA^Drug allergy|PEN^Penicillin^RXNORM|MO^Moderate|Rash|UP|ALG0001^CITYHOSP

What systems do with it

The sender is usually an EHR, allergy module, or medication safety system. Receivers may update allergy lists in pharmacy, dietary, clinical decision support, chart repositories, portals, and integration engines that route safety-relevant context with orders.

Because IAM can express update behavior, receivers should understand whether the feed is sending deltas, snapshots, deletes, or local action-code semantics. Do not guess.

How to read the structure

The core is MSH, EVN, and PID. Visit context in PV1 and PV2 is optional in the local data. The allergy detail lives in repeating IAM segments, where IAM-3 identifies the allergen, IAM-4 severity, IAM-5 reaction, IAM-6 action code, and IAM-7 the allergy unique identifier when available.

Implementation traps

Do not treat A60 like a simple text note. If IAM action codes or unique identifiers are ignored, deletes and corrections can turn into duplicate active allergies. Also decide how A60 interacts with AL1 snapshots in A01/A08 feeds; without a rule, the two workflows can overwrite each other.

Reference notes

The HL7 v2+ ADT_A60 page describes A60 as an adverse reaction update that uses IAM for action-code and unique-identifier mode updates. The HL7 v2+ IAM segment page describes IAM-6 as the action code and IAM-7 as the unique allergy identifier.