HL7 standard

The HL7 message format defines the standard data field, segment, and message layouts that are used in hospital communication systems. A complete implementation of the HL7 specifications is included with Cloverleaf, which defines these standards.

If message layouts follow these HL7 standards exactly, then the message formats can be used as provided.

If message layouts deviate in any way from the HL7 standard, then message formats must be user-configured, or assigned an HL7 variant. Each HL7 message-format variant that is created has a unique, user-specified name.

Use the HL7 Configurator to configure the variant. This tool provides the editing and display capabilities for defining and modifying data fields and assembling the segments for specific message layouts.

HL7 files reside in $HCISITEDIR/formats/.

When configuring the variant, always start with an HL7 standard as a base. Then, add or modify those fields, segments, and messages that differ from the standard. This procedure minimizes the amount of time spent configuring the message format.

A segment is a logical grouping of data fields. Each segment is given a name. For example, an ADT (Admissions, Discharge, and Transfer) message might contain these segments:

  • MSH (Message Header)
  • EVN (Event Type)
  • PID (Patient ID)
  • PV1 (Patient Visit)

Each segment is identified by a unique three-character code known as the Segment ID.

When using an Xlate, most messages do not have EVN-1 filled. If EVN-1 is required, then it is automatically filled with the event type when using an Xlate. If the field is optional, then it is not filled.

The MSH segment has certain required fields. If these fields are not set in a translation, then the outgoing message is created with default values. For example:

  • 0(0).MSH(0).00011 (or 00014 in 2.1): Processing ID: "P", where P is for production.
  • 0(0).MSH(0).00012 (or 00015 in 2.1): Version ID: the output version (for example, 2.1, 2.2, and so on).
  • 0(0).MSH(0).00009 (or 00012 in 2.1): Message Type: the output message type (for example, ORM, and so on).

If the interface requires these fields to be blank, then you can nullify them by copying @null to the field.

The HL7 v3 CDA version is an XML-based standard for the interchange of clinical documents. The CDA message definition is defined by schemas or DTDs.

Because CDA is an XML-based message, it is supported by importing the schemas/DTDs with the XML Package Manager.