HL7 glossary
Every bit of HL7 jargon, explained simply.
- ACK
- Acknowledgement. The reply a system sends to confirm it received and understood a message.
- ADT
- Admission, Discharge, Transfer. The family of messages announcing a patient’s movements.
- Champ
- A value inside a segment, separated by a vertical bar. You address it by its position, for example PID-5.
- Composant
- A subdivision of a field, separated by a caret. Example: a name "family^given".
- Délimiteur
- A character that splits the message: bar for fields, caret for components, tilde for repetitions.
- FHIR
- Fast Healthcare Interoperability Resources. The modern version of HL7, built on web tech (REST, JSON). Coexists with v2.
- HL7
- Health Level Seven. A messaging standard that defines how health systems exchange information.
- HL7 v2
- The historical version of HL7, recognizable by its vertical bars. Installed in almost every hospital in the world.
- Interface engine
- Middleware (Mirth, Cloverleaf…) that receives, transforms and routes messages between systems that do not natively talk to each other.
- LOINC
- A universal coding system for tests and observations. Often used in OBR-4 and OBX-3 to name a test.
- MLLP
- Minimal Lower Layer Protocol. The most common way to carry an HL7 v2 message over the network, with an acknowledgement.
- MSH
- Message Header. The first segment of every message: who sends, to whom, when, and what type of message it is.
- OBR
- Observation Request. The segment describing the test ordered or performed. It heads a group of OBX results.
- OBX
- Observation/Result. The segment of a single result: what, how much, in which unit, normal or not.
- ORU
- Observation Result. The message carrying results, for example a sleep study report.
- PID
- Patient Identification. The segment carrying the patient’s identity: name, date of birth, identifiers.
- Segment
- A line of a message, identified by a three-letter code (MSH, PID, OBX). Each segment groups one kind of information.
- Trigger event
- The event that triggers a message. Coded after the type, for example A01 (admission) in ADT^A01.