Biomedical Engineering Reference
In-Depth Information
Specifi cally:
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PID identifi es this as a patient identifi er segment.
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Segments are composed of fi elds, which are delimited by the pipe (|)
character.
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Fields one and two are blank, which is why there are three pipe
characters in a row.
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Field three is the patient identifi er, which in this example is '921342'.
This fi eld may have additional information as to how this identifi er
was generated.
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Field fi ve is the patient name. This fi eld is of type XPN, or extended
person name. This type of fi eld can be further broken down into
components (separated by the caret symbol '^' for components and
the ampersand '&' for subcomponents). With this type the fi rst
component is family name and the second given name.
This is an extremely simple example of an HL7 V2.x message. The entire
specifi cation for V2.6 messaging spans 27 documents. HL7 Version 3
(V3) has made a number of improvements, including embracing XML
for data communication over delimiters. It also went beyond cosmetic
changes and developed a semantic ontology for the transmission of
medical data between systems. The HL7 reference implementation model
(RIM) defi nes a core set of objects and message life cycles which they
intend to use as a base model for any message communication between
clinical systems, similar to a set of mathematical axioms.
The RIM is not simply an academic exercise, but is critical to
interoperability. This is because in any sort of complex communication,
context is vital. In verbal communication, words and phrases taken out
of context completely lose their meaning. The same is true in
communication between medical systems. For example, consider the
medication associated with a patient. Does this mean that the patient is
currently taking this medication, or has this medication been ordered for
this patient, or does this patient have an allergy to this medication?
Simply associating patient and medication together without context is
meaningless. The RIM forms the core foundation to give context to these
data points.
One of the more interesting standards coming out of HL7 V3 is the
CDA, especially for its application in analytics. Previously, most of the
clinical information has been kept in narrative form in clinical documents
such as history and physicals, operative reports, discharge summaries,
and so on. As these documents are in text form, it is diffi cult to derive
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