Table 2.
Comparison of CCR and CDA
| Category | Similarities | Differences | Assessment |
|---|---|---|---|
| Purpose and scope | Both provide a mechanism for creating medical documents in a human-readable and, where possible, machine-interpretable format. | CCR focuses on patient summary information. | Authors of this article prefer the CDA approach because of: |
| CDA has a much larger scope, accommodating any kind of medical document. | 1. Explicit support for use in multiple document exchange scenarios other than the transport of a patient health summary | ||
| CCR thus does not provide a formal mechanism for defining specialized CCR document types (e.g., discharge summaries, progress notes). | 2. Ability to define templates for specific use cases | ||
| By contrast, a patient summary is just one of many potential uses of the CDA standard and may be specified using a CDA “template.” | 3. Use of standard components (e.g., data types, information models) based on input from many different stakeholders from various HL7 committees | ||
| Because CDA was created by HL7, CDA is one of the HL7 version 3 family of standards; as such, its components (e.g., data types, information models) can be reused across other HL7 version 3 standards (e.g., messages). | |||
| Development methodology | Conducted at SDOs (ASTM for CCR, HL7 for CDA) | CCR does not explicitly consider use cases but was developed with direct clinician involvement. | The CCR methodology is most likely faster to implement. In the authors' opinion, the CDA model appears more robust in its ability to handle more complex details and extensions. |
| HL7 version 3 methodology explicitly considers use cases; HL7 uses a robust, balloted, consensus-driven development methodology. | |||
| Difficulty of use and implementation | Both CCR version 1a and CDA R2 are fairly complex (as opposed to CCR version 1, which was much more straightforward to understand and implement). | Effort used to implement CCR version 1a cannot be easily leveraged for meeting other standards-based communication needs: the components used (e.g., data types, information models, vocabulary specifications) need not be standard components, but they can be standards based (e.g., LOINC, SNOMED CT). | HL7 approach is generally preferred by the authors (compared to CCR version 1a), but the lack of a level 3 implementation guide for the CDA is a relative weakness and adds to the complexity of any CDA implementation. |
| Both CCR version 1a and CDA R2 provide detailed implementation guides, with validation mechanisms (implementation guide for CCR; implementation guide plus Schematron schemas or XSLT style sheets for CDA). | Effort used to implement CDA R2 can be leveraged for other data exchange needs, as they are based on common HL7 version 3 components. | ||
| CCR does not provide a method for specifying specific document templates based on use cases (e.g., discharge summary, referral to cardiologist, patient health summary), whereas CDA provides an explicit method for doing this (see section below entitled “Ability to specify and support specific use cases”). Since CCR was pragmatically derived by clinicians, it is not clear which is better. | |||
| CCR provides an implementation guide that covers its entire scope of work; CDA provides implementation guide only up to level 2 (section constraints), although the CDA committee is currently working on defining an implementation guide for level 3 (detailed structured content level). | |||
| Extensibility | Both CCR and CDA use XML syntax. | CCR makes a point of not allowing any user-configurable fields and thus does not allow for local differences in implementation. | In the authors' opinion, the CDA provides greater adaptability and extensibility to meet the needs of local implementations. If one adheres to the more narrowly defined purpose of CCR, it is uncertain how significant this difference is. |
| CDA is adaptable and explicitly allows for local extensions and configurability. Because of its broad object-oriented approach to modeling, the HL7 CDA is able to meet local requirements, while still allowing mapping back to the standard. It is not clear how detrimental the lack of extensibility is for CCR when one adheres to its stated purpose. HL7 has potential to meet additional goals due to extensibility. | |||
| Ability to specify and support specific use cases | CCR does not provide a formal method for defining specialized document templates based on use cases; it was derived by clinicians to meet a specific purpose. | In the authors' opinion, the HL7 approach is preferable because it is widely applicable to multiple use cases and explicitly provides a mechanism for specifying document templates. Again, if one adheres to the more narrow goals of CCR, the advantage of HL7 may not be as great. | |
| CDA provides a concrete method for specifying document templates to be used for specific use cases. In the current implementation guides, the constraints for particular use cases can be defined using Schematron schemas (http://xml.ascc.net/schematron/). | |||
| Information modeling approach | Multitiered specification, going from just human readable to detailed, unambiguous machine-interpretable encoding. | CCR implements this concept using a CodedDescriptionType, where level 1 is a simple text string, level 2 is a coded simple text string, and level 3 is a coded simple text string plus structured representation. | It is difficult to say that one approach is superior over the other; however, in the authors' opinion, the use of a robust reference information model (RIM) makes the HL7 information modeling approach attractive. Furthermore, the HL7 RIM has been International Standards Organization-approved and is the basis for many other approved standards. |
| CDA implements this concept using specifications at level 1 (unconstrained CDA specification), level 2 (section-level templates defined), and level 3 (entry-level templates defined). | |||
| Multiple miscellaneous differences (e.g., how addresses are modeled, how vocabularies are specified). |
CCR = Continuity of Care Record; CDA = Clinical Document Architecture; HL7 = Health Level 7; SDO = standards development organization; R1 = release 1; R2 = release 2; SNOMED CT = Systematized Nomenclature of Medicine Clinical Terms; LOINC = Logical Observation Identifiers Names and Codes; ASTM = American Society for Testing and Materials.
