XML, HL7 Messaging and the Clinical Document Architecture.

XML, HL7 Messagingand the Clinical Document Architecture

Contents

• Introduction to XML

• Introduction to Heath Level 7 (HL7)

• HL7 messaging, current and future

• HL7 Clinical Document Architecture (CDA)

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

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 <emph>metadata</emph> and "primary" data

Embedded "tag" Tag content

Heritage of Generalized Markup Languages

SGML

Internal workat IBM

TeX, nroff, troff

Many special-purpose markup

languages

HTML

XML

Many special-purpose markup

languages

1984

~1990

1998

XHTML

Frameworks

Implementations

Tag formatsDTD formatProcessing rules

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

XML Document Detail

<procedure cpt="1234"><pat_phys pnum="abcd">

<firstName>Elmer</firstName><lastName>Fudd</lastName><degree>M.D.</degree>

</pat_phys><proc_name>Upper endoscopy of gizzard</proc_name><proc_date>09/09/1999</proc_date><location name="ER"/>

</procedure>

Element name AttributeOpening tag

Closing tagSingleton tag

Content

HL7Health Level 7

• 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

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

"Level Seven"

A protocol for the exchange of health care information

ISO-OSI Layered Protocol Model

1 Physical 1 Physical 2 Data Link 2 Data Link 3 Network 3 Network 4 Transport 4 Transport

Communication

5 Session 5 Session 6 Presentation 6 Presentation 7 Application 7 Application

Function

HL7 Transactional Model

(external) admitevent

trigger event

network

sendHL7 A01 msg

receive HL7 ACK msg

ADT system

Lab system

Receive A01,send ACK

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Current Message-Router-Based Interfaces

HL7 Abstract Messages

• Identifies data fields

• Describes error conditions

• DOES NOT describe the byte string contained in the message.

Admit Message

MSH|^~\&|ADT1|MCM|LABADT|MCM|198808181126|SECURITY|ADTÂ01|MSG00001|P|2.3|<cr>

EVN|A01|198808181123||<cr>

PID|||PATID1234^5^M11||JONES^WILLIAMÂÎII||19610615|M||C|1200 N ELM

STREET^^GREENSBORO^NC^27401-1020|GL|(919)379-1212|(919)271-3434||S||

PATID12345001^2^M10|123456789|987654^NC|<cr>

NK1|JONES^BARBARA^K|WIFE||||||NK^NEXT OF KIN<cr>

PV1|1|I|2000^2012^01||||004777^LEBAUER^SIDNEY^J.|||SUR||||ADM|A0|<cr>

segments, fields, components & subcomponents

Variability in HL7 Interfaces

• Site 1:OBX|1|CE|ABOÂBO GROUP||O^Type O|

• Site 2:OBX|1|CE|BLDTYPÂBO GROUP||TYPEO^Type O|

• Site 3:OBX|1|CE|ABOTYPEÂBO GROUP||OPOS^Type O|

"when you've seen one HL7 interface you've seen one HL7 interface"

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

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

Reference Information Model (RIM)

Observation_intent_or_orderpatient_hazard_codereason_for_study_cdrelevant_clinical_information_txtreporting_priority_cdspecimen_action_cd

Clinical_observation

abnormal_result_ind : IDlast_observed_normal_values_dttm : DTMnature_of_abnormal_test ing_cd : CEclinically_relevant_begin_dttm : DTMclinically_relevant_end_dttm : DTMobservation_value_txt : NMprobability_number : NMreferences_range_text : STvalue_units_code : CE

Assessment

Healthcare_service_providerspecialty_cd : CNE

Stakeholder_identifierid : STidentif ier_type_cd : ID

Organizationorganization_name_type_cd : CNEorganization_nm : STstandard_industry_class_cd 0..*

0..1 is_a_subdivision_of

0..*

has_as_a_subdivision

0..1

Person

birth_dttm : DTMgender_cd : CNEmarital_status_cd : CNEprimary_name_representation_cd : CNEprimary_name_type_cd : CNEprimary_prsnm : PNrace_cd : CNE

Individual_healthcare_practitionerdesc : TXpractitioner_type_cd : CNE

1

0..1

takes_on_role_of1

is_a_role_of0..1

Stakeholderaddr : XADphon : XTN

0..*

1

is_assigned_to0..*

is_assigned1

Healthcare_provider_organization

0..1

1

is_a_role_of0..1

takes_on_role_of

1

Collected_specimen_samplebody_site_cd : CEcollection_end_dttm : DTMcollection_start_dttm : DTMcollection_volume_amt : CQhandling_cd : IDid : IIDmethod_of_collection_desc : TXspecimen_addit ive_txt : STspecimen_danger_cd : IDspecimen_source_cd : CE

0..*1

is_collected_by

0..*

collects

1

Patient

ambulatory_status_cdbirth_order_numberliving_arrangement_cdliving_dependency_cdmultiple_birth_indnewborn_baby_indorgan_donor_indpreferred_pharmacy_id

0..1

1

is_a_role_of

0..1takes_on_role_of

1

0..*

0..1

has_a_primary_provider

0..*is_the_primary_provider_for

0..1

0..*

0..1

is_sourced_from0..*

is_source_for0..1

Active_participation

participation_type_cd : ID

0..1

0..*

participates_in0..1

has_as_participant0..*

Master_patient_service_location

addr : XADemail_address : XTNid : IDnm : STphon : XTN

1..*

0..*provides_patient_services_at

1..*

provides_services_on_behalf_of0..*

0..*

0..1

is_included_in

0..*

includes 0..1

0..1

0..*

is_primary_facility_for0..1

has_as_primary_facility

0..*

Target_participationparticipation_type_cd : CE

0..1

0..*

is_target_of

0..1

has_as_target0..*

0..1

0..*

is_target_of

0..1

has_as_target

0..*

0..1

0..*

is_target_for0..1

has_as_target

0..*

Service_intent_or_orderfiller_order_id : IIDfiller_txt : TXorder_idorder_placed_dttm : DTMorder_quantitytiming_qt : TQplacer_order_id : IIDplacer_txt : TXreport_results_to_phone : XTNintent_or_order_cd : ID

0..* 0..1

participates_in

0..*

has_as_participant

0..1

1..*

0..1

is_target_of

1..*

has_as_target

0..1

1

0..*

is_entry_location_for

1

is_entered_at

0..*

Master_service

method_cd : CEmethod_desc : TXservice_desc : TXtarget_anatomic_site_cd : CEuniversal_service_id : CE

0..*

1

is_an_instance_of

0..*

is_instantiated_as

1

Service_event

service_desc : STservice_event_descspecimen_received_dttm : DTMname : CE

0..*

0..1

participates_in0..*

has_as_active_participant

0..1

0..*

0..1

is_performed_at

0..*

is_location_for

0..1

0..*

0..1

is_target_of

0..*

has_as_target

0..1

0..1

0..*

is_fulfilled_by0..1

fulfills0..*

1

0..*

is_delivered_during1

delivers

0..*

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

HL7 2.3 Message Format

HL7 v3 Message Format

HL7 Clinical Document Architecture (CDA)

• 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

A multilevel representation of medical documents that can be passed as messages and which make up the medical record.

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

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

CDA Level 1 Markup

Header & "wrapper"

Clinical Documentas text

CDA Level 2 Markup

Header & "wrapper"

Clinical Documentwith structural markup(main sections)

CDA Level 3 Markup

Header & "wrapper"

Clinical Documentwith detailed markupincluding local extensions

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

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

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?

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.