HL7 Messages

HL7 Messages - Health Level 7

An HL7 message consists of the following data elements.

All HL7 messages are made up of segments, composites and primitive data types.

An HL7 message consists of the following data elements: Message type, Message event and Message structure.

Message type

An HL7 message type is a unique identifier of the purpose of a message. Every message must contain a message type as way to declare the purpose of the message. For example, an HL7 message with the message type id of ADT is a unique message ID to Patient Administration.

The message type is listed in the message header segment of every HL7 message.

Message event

The message event, which is sometimes called the message trigger, is an identifier to the context in which the HL7 message was generated. The message event consists of an upper case letter and two digits. For example, A01 is for an admission/visit notification HL7 message and A61 is the message event for an HL7 message for changing consulting doctor. Both A01 and A61 are used with ADT messages.

Event type is listed in the message header segment of every HL7 message.

Message structure

The message structure is a data structure that expresses an association of a message type with an event for a class of HL7 messages. Each message structure also contains a unique ID.

It structurally consists of a well-defined list of HL7 segments. Segments can be optional, and can repeat. There is no limit on how many times a segment can repeat within an HL7 message.

HL7 messages are event driven and sent when an action occurs. HL7 messages "should" be formed and transmitted based on the HL7 standard - also known as the "non-standard standard". As a result of slight inconsistancies in messages, many healthcare organization use Integration Engines or HL7 Tools in order to help translate different flavors of HL7.

Example HL7 Message:

MSH|^~\&|GHH LAB|ELAB-3|GHH OE|BLDG4|200202150930||ORU^R01|CNTRL-3456|P|2.4
PID|||555-44-4444||EVERYWOMAN^EVE^E^^^^L|JONES|19620320|F|||153 FERNWOOD DR.^^STATESVILLE^OH^35292||(206)3345232|(206)752-121||||AC555444444||67-A4335^OH^20030520
OBR|1|845439^GHH OE|1045813^GHH LAB|15545^GLUCOSE|||200202150730|||||||||555-55-5555^PRIMARY^PATRICIA P^^^^MD^^|||||||||F||||||444-44-4444^HIPPOCRATES^HOWARD H^^^^MD
OBX|1|SN|1554-5^GLUCOSE^POST 12H CFST:MCNC:PT:SER/PLAS:QN||^182|mg/dl|70_105|H|||F