CDA is an XML-based, electronic standard used for clinical document exchange that was developed by Health Level Seven. CDA conforms to the HL7 V3 Implementation Technology Specification (ITS), is based on the HL7 Reference Information Model (RIM), and uses HL7 V3 data types. It was known earlier as the Patient Record Architecture (PRA).

CDA is a flexible standard and is unique in that it can be read by the human eye or processed by a machine. This is due to its use of XML language, which also allows the standard to be broken into two different parts. A mandatory free-form portion enables human interpretation of the document, while an optional structured part enables electronic processing (like with an EMR system). Text, images and even multimedia can be included in the document.

A CDA document could be, for example, any of the following: discharge summary, referral, clinical summary, history/physical examination, diagnostic report, prescription, or public health report. In short, any document that might have a signature is a viable document for CDA.

Implementation of CDA

CDA does not specify a transport mechanism and can be utilized within a messaging environment or outside of it. Transport methods can include HL7 V2, HL7 V3, DICOM, MIME-encoded attachments, HTTP, or FTP. CDA is flexible enough to be compatible in a wide range of environments, and can be stored as a document in a computer system (permanently or temporarily) or can be transmitted as the content of a message.

In current practice, very few providers or vendors in the United States actually utilize CDA due to its relative newness and a lack of mandate to utilize it. However some examples of international implementations of CDA include: PICNIC (Ireland, Denmark, Crete), SCHIPHOX (Germany), MERIT-9 (Japan), Staffordshire EHR (United Kingdom), and Regional Health Information System – Satakunta Macropilot (Finland).

CDA Structure

CDA is an XML document that consists of a header and body. It is presented in this format:

• Header – includes patient information, author, creation date, document type, provider, etc.
• Body – includes admission details, diagnosis, patient details, medications, follow-up, etc. Presented as free text in one or multiple sections, and may optionally also include coded entries.

CDA has three levels of document definition, with Level One providing the least structure and Levels Two and Three providing greater structure:

• Level One – the root hierarchy, and the most unconstrained version of the document. Level One supports full CDA semantics, and has limited coding ability for the contents. An example of a level one constraint on document type would be "Discharge Summary."
• Level Two – additional constraints on the document via templates at the "Section" (free text) level. An example of a level two constraint on document type would be "Emergency Department Discharge Summary."
• Level Three – additional constraints on the document at the "Entry" (encoded content) level, and optional additional constraints at the "Section" level.

CCD (Continuity of Care Document), an ANSI standard approved in 2007, is built on CDA elements by using a detailed set of constraints. More information about CCD can be found here or in our CCD white paper (PDF). More information about CDA can be found on the HL7 website.