XML, HL7 Messaging and the Clinical Document Architecture

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XML, HL7 Messagingand the Clinical Document
Architecture
2
Contents

• Introduction to XML
• Introduction to Heath Level 7 (HL7)
• HL7 messaging, current and future
• HL7 Clinical Document Architecture (CDA)

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Generalized Markup Languages

• Markup identifies structural elements of a
  document rather than specific formatting features
• Markup is expressed as standard text sequences
  (markup "tags")
• Formatting instructions are applied separately to
  the specified document elements
• Markup tags can be human-readable

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Markup Expresses Metadata

• Documents naturally have content and metadata
• Metadata may help specify
• Meaning of data (e.g., standard coding)
• Arrangement of data (display)
• Correct use of the data (business rules)
• Context and relationships between data elements
• Example of display markup
• Documents contain ltemphgtmetadatalt/emphgt and
  "primary" data

Tag content
Embedded "tag"
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Heritage of Generalized Markup Languages
Internal work at IBM
TeX, nroff, troff
SGML
Tag formats DTD format Processing rules
Frameworks
1984
Many special- purpose markup languages
XML
1998
HTML
XHTML
1990
Many special- purpose markup languages
Implementations
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Extensable Markup Language (XML)

• HTML originally specified structural components
  of documents
• HTML has evolved to become a presentation syntax
• SGML is complex and requires complex processing
  software
• XML is a simplified version of SGML designed for
  electronic document archiving and exchange
• Allows creation of special-purpose markup
  languages
• Can represent a variety of data structures and
  semi-structured data as well as metadata
• Arbitrary tag nesting, recursion and granularity
• Human-readable and machine readable
• Expected to be useful for creation of special
  purpose data-interchange standards as well as
  document structuring

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XML Document Detail
Opening tag
Element name
Attribute
ltprocedure cpt"1234"gt ltpat_phys
pnum"abcd"gt ltfirstNamegtElmerlt/firstNamegt ltlas
tNamegtFuddlt/lastNamegt ltdegreegtM.D.lt/degreegt lt/p
at_physgt ltproc_namegtUpper endoscopy of
gizzardlt/proc_namegt ltproc_dategt09/09/1999lt/proc_d
ategt ltlocation name"ER"/gt lt/proceduregt
Content
Singleton tag
Closing tag
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HL7Health Level 7
Organized to create standards for the exchange,
management and integration of data that supports
clinical patient care and the management,
delivery and evaluation of healthcare services

• Founded by healthcare providers in 1987
• Version 1.0 late in 1987
• Version 2.0 late in 1988
• Versions 2.1, 2.2 and 2.3 published in 1990,
  1994 and 1997 ANSI standards
• Pragmatic approach
• Work on Version 3 (XML-based) is ongoing

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"Level Seven"
A protocol for the exchange of health care
information
ISO-OSI Layered Protocol Model
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HL7 Transactional Model
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Current Message-Router-Based Interfaces
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HL7 Abstract Messages

• Identifies data fields
• Describes error conditions
• DOES NOT describe the byte string contained in
  the message.

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Admit Message
segments, fields, components subcomponents
MSH\ADT1MCMLABADTMCM198808181126SECURIT
YADTA01MSG00001P2.3ltcrgt EVNA01198808181123
ltcrgt PIDPATID12345M11JONESWILLIAMAIII
19610615MC1200 N ELM STREETGREENSBORONC27
401-1020GL(919)379-1212(919)271-3434S PATI
D123450012M10123456789987654NCltcrgt NK1JONES
BARBARAKWIFENKNEXT OF
KINltcrgt PV11I2000201201004777LEBAUERSID
NEYJ.SURADMA0ltcrgt
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Variability in HL7 Interfaces

• Site 1
• OBX1CEABOABO GROUPOType O
• Site 2
• OBX1CEBLDTYPABO GROUPTYPEOType O
• Site 3
• OBX1CEABOTYPEABO GROUPOPOSType O

"when you've seen one HL7 interface you've seen
one HL7 interface"
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HL7 v2.x is not Plug and Play

• Cost of installing an HL7 interface 2-4 weeks of
  analyst time
• Issues
• Different implicit information models
• Misunderstanding of specifications
• No vocabulary to describe conformance except by
  detailed specs
• Significant local demands on vendors

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Goals for Version 3

• Substantially reduce interface development time
• Clarify spec for messages
• Create a specified information model
• Method for conformance specification
• Support modern communications infrastructures
• Reference Information Model (RIM)
• Coherent shared information model
• Includes all content of HL7 messages
• Provides consistency to messages across usage
  settings

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Reference Information Model (RIM)
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Advantages of XML for Message Formatting

• The syntax handles recursion and nesting
• Variably nested structures to arbitrary depth
• More flexible than segments, fields, components
  subcomponents
• Objects (including contained objects) can be
  represented
• Relational structures can be represented
• Simple syntax, easy to debug (human readable)
• Software tools (parsers, etc.) are generally
  available
• Language- and platform-independent
• Compatibility with other industries

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HL7 2.3 Message Format
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HL7 v3 Message Format
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HL7 Clinical Document Architecture (CDA)
A multilevel representation of medical documents
that can be passed as messages and which make up
the medical record.

• Level 1 XML-coded header
• Contents may be flat or tagged text
• Level 2 Coded document sections
• Generic architectural DTD with multiple derived
  DTDs
• Level 3 Coded content
• Text tagging based on RIM
• Generic architectural DTD with multiple derived
  DTDs
• Initial focus is documents used directly in
  clinical care

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Definition of a Document

• Persistence
• Defined by local and regulatory requirements
• Stewardship
• Maintained by an organization or person
• Authentication
• A collection of information that is to be legally
  authenticated
• Wholeness
• Legal authentication applies to the document as a
  whole and not to parts of the document out of
  context. The document also establishes a context
  for use of the contained information.
• Human readability

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Advantages of XML for Document Management

• Adaptable to unstructured and semi-structured
  data
• Tagging does not destroy the document or its text
  flow
• The text of the document can be recovered by
  ignoring the tags
• Tagged document are human readable
• If tagging is well-documented and/or tags are
  logically named, XML documents will remain
  readable over the long term

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CDA Level 1 Markup
Header "wrapper"
Clinical Document as text
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CDA Level 2 Markup
Header "wrapper"
Clinical Document with structural markup (main
sections)
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CDA Level 3 Markup
Header "wrapper"
Clinical Document with detailed markup including
local extensions
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Why Not Standardize DTDs?

• DTDs support local processes
• Single documents may use multiple DTDs
• Achieving consensus on details is lengthy
• DTDs evolve with local needs
• Strategy
• Create generic architectural DTDs
• Allow local extension
• Local extensions can be ignored when necessary

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Key Header Elements

• ID, set ID, version, addendum vs. replacement
• Fulfills order
• Document type (LOINC)
• Origination time
• Confidentiality level
• Patient encounter
• Service actors (care providers individuals and
  organizations)
• Authenticator, legal authenticator, originator,
  intended recipient, originating organization,
  provider, transcriptionist
• Service target (living or inanimate)
• If patient, one and only one

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Structural Markup

• HTML-like (captions/headings, paragraphs, lists,
  tables)
• Recursive relationships
• Content tag generic identifier and target for
  text sequences
• Coded entry standard vocabulary entry, can be
  targeted to a text span defined by content tags
• Generic design yields limited ability to specify
  structure of particular document types (schemas?)
• Complex style sheets for particular documents?

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Summary

• XML is a flexible framework for creating tag
  vocabularies that add metadata to textual
  documents
• HL7 is a core standard in healthcare systems
  communications that has strengths and also
  specific weaknesses
• A new version of the HL7 messaging standard
  attempts to address those weaknesses through
  definition of a reference information model and
  XML message formatting
• HL7 has also defined a generic XML standard for
  clinical documents that is intended to improve
  the structure, accessibility and longevity of the
  electronic medical record.