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HL7 Interface
1. Introduction to HL7 V2.5
Standard
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2. Interoperability : Ability of two or systems or
components to exchange information and use
the information that has been exchanged
[ source : IEEE Standard Computer Dictionary
: A Compilation of IEEE Standard Computer
Glossaries, IEEE, 1990]
Functional interoperability - Message format
and content
Semantic interoperability - Terms (SNOMED-CT,
LOINC), units
Service (Business) Interoperability – SOA, HISA
Vision : Plug and play (PnP)
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3. Computers work by matching
Cannot handle the unexpected
Easier to send than to receive
Testing, Testing, Testing
(N2 - N)/2 = Number of interface N
Benefits of
Standards
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4. Reduce Cost
Reduce Risk
Competition (avoidance of lock-in)
Change control (real costs of upgrades)
Quality (leveling up)
Compliance testing
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5. OSI Level 7
Organization
Standards
HL7 is a Language (s)
• Syntax (Grammar)
• Semantics (Words)
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6. Layer 7 - Application - network processes for
application
Layer 6 - Presentation - Data Representation
Layer 5 - Session - Interhost communication
Layer 4 - Transport - End-to-end connections
Layer 3 - Network - Addresses and best path
Layer 2 - Data Link - Access to media
Layer 1 - Physical - Binary transmission
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9. 1988 - present (backwards compatible)
Very widely used in hospitals
Position-dependent syntax
EVN||20040627||||20040601
PID|||567890^^^CXH^PI~9999999484^^^NHS
Local tailoring of Z-segments
“If you have seen one implementation, then
you have
seen one implementation”
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10. Message
Segment
Field
Data Type (may repeat)
Component
SubComponent
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11. MESSAGE SYNTAX
SEG –1..1
[ SEG ] – 0..1
{ SEG } – 1..*
{ [ SEG ] } – 0..*
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12. DELIMITERS
• Defined at start of MSH segment
• Segment terminator is carriage return (hex 0D)
| (vertical bar): field separator
~(tilde): repetition separator
^ (caret): component separator
& (ampersand): subcomponent separator
(backslash): escape character
Always start
MSH|^~&|MegaReg|XYZHospC|SuperOE| |2.5|
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13. 1. Introduction 11. Patient Referral
2. Control 12. Patient Care
3. ADT 13. Laboratory Automation
4. Orders 14. Application Management
5. Query 15. Personnel Management
6. Financial Management
7. Observation Reporting
8. Master Files
9. Medical Records
10. Scheduling
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15. HL7 V2.4, V2.5, V2.5.1(Lab test results),
V2.6, V2.7(Device communication)
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16. Chapter 2 of the HL7 V2.x Standard
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17. Defines the generic rules that apply to all
messages
The Key: How to read the rest of the
specification
HL7 Encoding Rules: what the !@#$ are those
|^& in my data stream?
The programming procedures required to
exchange all messages
Standard conformance profiling rules for
message
specification
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18. Expects ISO OSI Level 7. If not, lower level
protocols are available:
Ad hoc w/o basic transport (RS-232) – LLP
Robust export but not level 7(TCP-IP)-MLLP
Expects the following:
Error free transmission
Character conversion
No assumed maximum message length
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21. A real world event that necessitates an
exchange of information.
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22. An atomic unit of data transferred between
systems.
A Message Type defines its domain.
A Trigger Event defines the reason for the
exchange.
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23. A 3-character code contained within each
message that identifies its type or domain.
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24. One message type can have many different
trigger event codes.
A trigger event code may not be associated
with
more than one message type.
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25. A message is comprised of a group
of segments in a defined sequence.
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26. Information about the message
(MSH)
Information about the patient
PID, AL1, PV1)
Information about the order
(ORC, order detail segment,
OBX, BLG)
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27. Segments of a message:
are identified by a unique three
character code known as the
Segment ID.
Can be required
MSH is ALWAYS required!
May be optional [..]
May repeat {…}
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28. A logical grouping of data field PID segment
Definition (Partial)
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29. SEQuence – the order of an element within the
segment
Max LENgth
Data Type
OPTionality:
R - Required - Too few of these!
O- Optional- Too many of these !
C- Conditional-Based on what?
X- Don’t use
B- Retained for backwards compatibility
W-Withdrawn
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30. RP/# = Repetition:
N-No or Y-Yes; may designate number of repetitions
TBL# = Table Number
A unique identifier for a table of values used by the
data element
HL7 defined values
User defined values
Externally defined values
ITEM# - a unique identifier for the HL7 data
element
ELEMENT NAME
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31. Messages are made up of segments
which are made up of fields which may have
components which may have sub-components.
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32. An HL7 field is a set of characters defined by an
HL7 data type. For example, marital status.
PID.15 (data type CWE)
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33. A field entry may also have parts called
components. For example, the patient’s
name has components such as
last name
first name
middle name or initial
Components may be further divided into
sub-components.
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35. To determine the exact representation of an abstract
message, one applies the HL7 encoding rules defined in
Chapter 2 to the abstract definition from the functional
chapter (example - Chapter 3, Patient Administration).
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37. In a message certain encoding characters delimit the
constructs.
The Segment Terminator <CR>
The Field Separator |
The Component Separator ^
The Sub-Component Separator &
The Repetition Character ~
The Escape Character
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38. The Encoding Characters are specified immediately
following the segment ID in the MSH Segment.
With the exception of the segment terminator,
delimiter values are at the discretion of the sender.
Most senders use the suggested values.
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39. The HL7 field separator marks the beginning of a
data field within an HL7 segment.
It always follows the segment ID to indicate the
first data field in the segment.
|
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40. Used to separate adjacent components within a field.
The data type defines whether a field has
components.
^
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41. Used to separate occurrences of a repeating field.
The “repetitions” are of a common structure (like rows
in a database) defined by the data type. The content of
each repetition may be (and usually is) different.
~
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42. Used in alphanumeric fields defined by data
types ST, TX or FT
Used for highlighting
Used to escape the other delimiters
Used for hex character representation
Must both precede and follow the
character(s) being escaped
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44. Used to separate adjacent subcomponents.
The data type defines whether the components of a
field have subcomponents.
When a component of a data type is itself a data type
with components, its parts will be expressed as
subcomponents of the full data type.
&
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45. Is the last character of EVERY segment.
Is ALWAYS the ASCII CR character (hex 0D).
Is NEVER omitted.
Can NEVER be changed.
<CR>
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49. If components, subcomponents, or repetitions at the
end of a data field are ‘not present’, their separators
may be omitted
If no more fields are present in a segment, the data
field separators may be omitted
Padding doesn’t violate the rules, it’s just not good practice!
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50. End each segment with the REQUIRED
segment terminator
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51. Rule 1: Ignore the unexpected
Rule 2: If it’s not there, assume it’s not
present.
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52. Ignore segments, fields, components,
subcomponents, and repetitions of a field that
are present but not expected.
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53. Treat fields, components, subcomponents, and
repetitions that are expected but not sent as not
present.
DON’T break the interface
DO return an ERR segment in the acknowledgment
message for each required field that is missing
Treat segments that were expected but not sent
as
consisting entirely of fields that were not sent.
Example: If the PR1 procedure segment is not sent on
a discharge, assume that procedure info is not present -
do NOT assume it’s NULL.
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54. New messages may be introduced in subsequent
versions.
New segments may be introduced and placed
anywhere in an existing message structure in
subsequent versions.
In subsequent versions new F/C/S/R - can only be
introduced at the end of a segment, field,
component, or repetition list.
Data types can only be extended in subsequent
versions by adding components to the end.
Non-repeating field can become repeating, but first
repetition meaning should remain the same.
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55. Retained for backwards compatibility only”
designates fields no longer recommended for
use, but retained as place holders. These
fields may need to be valued to support prior
versions.
Obsolete message elements may be
withdrawn when they are no longer referred
to by other parts of the Standard: e.g.,
superseded data types such as CE.
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57. Here are the ones that occur most frequently:
Alphanumeric (ST TX FT SRT)
Numeric (CQ MO NM SI SN)
Identifier (ID IS HD EI RP PL PT
VID)
Date/Time (DT TM DTM)
Coded Values (CF CN CX XCN
CNE CWE)
Demographics (XAD XPN
XON XTN SAD FN)
Price Data (CP)
ADT/Finance (FC)
Extended Queries (QSC QIP RCD)
Master Files (DLN JCC VH)
Medical Records (PPN)
Time Series (DR RI SCV TQ)
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![ Interoperability : Ability of two or systems or
components to exchange information and use
the information that has been exchanged
[ source : IEEE Standard Computer Dictionary
: A Compilation of IEEE Standard Computer
Glossaries, IEEE, 1990]
Functional interoperability - Message format
and content
Semantic interoperability - Terms (SNOMED-CT,
LOINC), units
Service (Business) Interoperability – SOA, HISA
Vision : Plug and play (PnP)
Tuesday, June 09, 2009 2](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)