^A08
ADT^A08 — Update Patient Information
Sent whenever patient demographics or visit information changes for an existing encounter. This is a delta update — the receiving system should update its patient record with the new information without creating a new encounter.
When Is This Sent?
When any demographic field changes: name correction, address update, insurance change, attending physician reassignment, or any PID/PV1 field modification during an active encounter.
Real-World Usage
A08 is typically the highest-volume ADT message type by count. Every registration update, even minor ones like correcting a misspelled name, generates an A08. Downstream systems that don't process A08 will have stale patient demographics. The challenge is that A08 carries the full patient record — receiving systems need to determine which fields actually changed.
Message Structure
Segment names link to their field-level reference pages.
| # | Segment | Purpose in this message | Req | Repeat |
|---|---|---|---|---|
| 1 | MSH | Message header with ADT^A08 in MSH.9 | R | — |
| 2 | EVN | Event type with A08 trigger | R | — |
| 3 | PID | Complete updated patient demographics | R | — |
| 4 | PV1 | Complete updated visit information | R | — |
| 5 | PD1 | Updated additional demographics | O | — |
| 6 | NK1 | Updated next of kin | O | Yes |
| 7 | AL1 | Updated allergy list | O | Yes |
| 8 | DG1 | Updated diagnoses | O | Yes |
| 9 | IN1 | Updated insurance | O | Yes |
Example Message
Realistic example with fake patient data. Paste into the HL7 Message Viewer to explore interactively.
1MSH||^~\&|EPIC|HOSPITAL_A|MIRTH_PROD|PACS|20260310150000||ADT^A08^ADT_A08|MSG00015|P|2.5.1 2EVN||A08|20260310150000 3PID||1||123456^^^HOSP_A^MR||Smith^Jonathan^M^^Mr.||19850315|M|||789 New Rd^^Springfield^IL^62703^US^H||2175551234^PRN^PH 4PV1||1|I|4A^201^1^^^HOSP_A||||1234^Ahmed^Dr.^Khalid|||MED|||||||||IP||||||||||||||||||||||||||20260310143000
Troubleshooting Scenarios
Demographic updates not propagating to downstream systems
Cause
Downstream systems are configured to only receive A01/A04 messages and are not subscribed to A08 events. Name and address corrections never reach the downstream record.
Fix
Add A08 to the subscription list for all downstream systems that need current demographics. This includes PACS, RIS, pharmacy, and any system that displays patient names to clinicians.
A08 update storms causing interface engine performance issues
Cause
The EHR sends an A08 for every field change, including trivial edits. During a batch import or registration drive, this can generate thousands of A08 messages per hour.
Fix
Implement deduplication logic in the interface engine: if multiple A08 messages arrive for the same patient within a short window (e.g., 5 minutes), only forward the last one. Also consider throttling A08 messages to downstream systems that update in batch anyway.
Common Confusions
ADT^A08 (Update patient info) vs ADT^A28 (Add person) / ADT^A31 (Update person). A08 updates an existing encounter. A28/A31 operate on the person-level record in the master patient index without creating or modifying an encounter. Use A08 during active visits; use A31 for demographic corrections when there's no active visit.
Related Message Types
Segment Reference
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