Overview of HL7 CDA

[CDA: Clinical Documents Architectural]

- A standards-setting organization, supported by vendor and provider

accredited by ANSI (American national standards Institute)

• develop by communication protocols widely used in the US and world wide:
• health care messaging standards
• standards for representing clinical documents (CDA)

Clinical document standards:

• why?
• to unlock the considerable clinical content currently stored in free-text clinical notes
• to compare the content from documents created on information systems of widely varying characteristics
• problem on clinical note: structure, underlying information models, degree of semantic encoding, use of standard healthcare; difficult to store and exchange docs with retention of standardize semantics over both time and distance

CDA: is a document markup standards that specifics the structure and semantics for clinical doc.

Design principle:

• give priority to documents generated by clinicians involved in direct patient care
• minimize the technical barriers needed to implement the standard
• many non-standardized clinical documents exist

- CDA facilitates documents standardization

• allow cost effective implementation across as wide spectrum of systems.
• support exchange human-readable documents between users with different levels of technical sophistication
• enable a wide range of post-exchange processing applications
• provide compatibility with a wide range of document creation applications
• use non-healthcare-specific standards where possible.
• promote longevity of all information encoded according to this architecture

- CDA documents should be

• Application - aNd platform- independent
• viewable and editable by number of tools

• Enable policy makers to control their own information requirements without extension to this specification
• an extensibility mechanism is defined in CDA to allow local implementation to represent information not formally represented in the standard.

CDA document:

- A defined and complete information object that can include text, image, sounds and other multimedia content.

- Can be sent inside an HL7 message or exist independently outside a transferring message.

CDA includes a hierarchical set of document specifications:

- A set of hierarchically related XML Document Type Definition (DTD) or schemas

- Envisioned for future releases of the CDA standard.

• There levels of hierarchy: CDA level one (top node), two and three
• The level only affects the degree to which
• clinical content can be machine procecciable in an exchange context
• clinical document specifications can impose constraints on content

L1 specs:

sufficiently detailed to represent largely narrative clinical notes.

intend to minimize the technical barriers to adoption of the standard while providing a gentle introduction to the RIM

Provision of deeper levels of the architecture will provide a migration pathway for implementers to iteratively add greater markup to clinical documents.

L2 specs

• set of templates or constraints that can be layered on top of the CDA l1 specs
• Template development require domain knowledge and professional societies; participation
• to ensure the created templates are are widely embraced and supported.
• liaison relationship with professional societies is needed.

L3 specs

• add additional RIM-derived markup to the CDA level 1 spec
• to enable clinical content to be formally expressed with RIM or formally expressed as HL7 V3 message, so that
• an order message can be extracted from a clinical document
• detailed representation of symptoms and findings can be obtained
• billing codes can be automatically extracted.

Technical overview of CDA

Has a header and a body

-header conveys the context in which the document was created, so as to:

- make clinical document exchange possible across and within institutions

- facilitate clinical document management

- facilitate compilation of an individual patient’s clinical documents into a lifetime EHR

- Body contains the informational statements that make up the actual content of the document.

Document information

• identify the document
• define confidentiality status
• describe relationship to other documents and orders

Encounter data

• describe the setting in wihc a documented encounter occurred.

Localization and transformation

Transformation issues:

• Due to syntactic limitation, or irresolvable semantic mappings
• Local instance in different order
• vs
• Source may be missing a required element
• CDA requires a globally unique document identifier
• Source having different vocabulary domains
• ‘male’ vs ‘M’
• Elements having different date type
• Source may be have coarser granularity (i.e. less detailed markup)