HL7 ADT
Admit, Discharge, Transfer messages
ADT is the family of HL7 v2 messages that communicate patient admissions, discharges, transfers, and demographic updates — the most common real-time feed in a hospital.
ADT (Admit, Discharge, Transfer) is the highest-volume HL7 v2 message family in most hospitals. ADT messages broadcast patient movement and demographic events — an admission (A01), transfer (A02), discharge (A03), registration (A04), pre-admit (A05), and demographic updates (A08), among many trigger events.
An ADT message is built from segments: MSH (message header), PID (patient identification), PV1 (patient visit), and often DG1 (diagnosis) and others. Downstream systems (labs, pharmacy, billing, and analytics) subscribe to the ADT feed to keep their patient context current in real time.
Because ADT carries identity and encounter context, it maps naturally onto FHIR: PID becomes a Patient resource, PV1 populates an Encounter, and a DG1 diagnosis surfaces as a Condition, which is exactly the translation modern FHIR-based apps and APIs depend on.
How this relates to Health1st
A live ADT^A01 is the canonical Health1st demo: PID → FHIR Patient, PV1 → Encounter, and DG1 (ICD-10 E11.9, Type 2 diabetes) → Condition — mapped by AI, validated against US Core, and reviewed by your team.
Related terms
HL7 v2 is the pipe-and-hat messaging standard that still carries most real-time clinical data between hospital systems — admissions, orders, results, and more.
FHIR is HL7's modern, web-native standard for exchanging healthcare data as modular JSON/XML resources over RESTful APIs.
US Core is the HL7 implementation guide that constrains FHIR resources into the specific profiles US regulation requires, binding them to USCDI data elements.
An EMPI resolves whether records from different systems refer to the same person, using probabilistic matching to link identities without a shared identifier.
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