In an HL7 message, each segment of the message contains one specific category of information, such as patient information or patient visit data. For example, consider the sample HL7 message that you saw in the previous section:
In an HL7 message, the name of each segment in the message is specified by the first field of the segment, which is always three characters long. This example message contains four HL7 segments: MSH, PID, NK1 and PV1. Different types of HL7 messages contain different HL7 segments. (For more information on the type of an HL7 message, see Determining the HL7 Message Type.)
Here is an example of a typical HL7 message:
PID||0493575^^^2^ID 1|454721||DOE^JOHN^^^^|DOE^JOHN^^^^|19480203|M||B|254 MYSTREET AVE^^MYTOWN^OH^44123^USA||(216)123-4567|||M|NON|400003403~1129086|
PV1||O|168 ~219~C~PMA^^^^^^^^^||||277^ALLEN MYLASTNAME^BONNIE^^^^|||||||||| ||2688684|||||||||||||||||||||||||199912271408||||||002376853
The HL7 segments in this example contain the following information:
- The MSH (Message Header) segment contains information about the message itself. This information includes the sender and receiver of the message, the type of message this is, and the date and time it was sent. Every HL7 message specifies MSH as its first segment.
- The PID (Patient Information) segment contains demographic information about the patient, such as name, patient ID and address.
- The NK1 (Next of Kin) segment contains contact information for the patient’s next of kin.
- The PV1 (Patient Visit) segment contains information about the patient’s hospital stay, such as the assigned location and the referring doctor.
Over 120 different HL7 segments are available for use in HL7 messages.