Document Templates
The article What is a CDA Template?,  introduces the template concept in CDA. In particular, it notes that C-CDA document templates define overall rules for an entire CDA document. This includes both rules that govern the CDA Header portion of a C-CDA document that adheres to the document template, as well as which section templates are required or are optional.

Header Templates
The templates defined by the C-CDA specification (more formally, the C-CDA implementation guide) are either document-level templates, section-level templates, or entry-level templates.

One important exception is the C-CDA template named US Realm Header template, which also informally goes by the names: US Realm General Header, US General Header, General Header Constraints, US C-CDA Header, and similar. Refer to The realmCode element, for a discussion of the “realm” concept in CDA and C-CDA.

In many ways, this special header template is very similar to a document template. Like with document templates, the template is applied to the ClinicalDocument root element of the document. Similarly, the identifier for the header template goes into the templateId element (refer to the article The templateId element, for additional information) that is located directly under the ClinicalDocument root element of a C-CDA document.

However, this special header template does not address any aspect of the CDA Body (the sections and entries of a CDA document). It only defines rules that govern the CDA Header.

Every C-CDA Document Asserts Compliance with the US Realm Header Template
Regardless of which C-CDA document template is selected for a given C-CDA document instance, that C-CDA document template states, as one of its conformance rules, that the header must adhere to the special US Realm Header template as well.

In other words, every C-CDA document must assert conformance to the US Realm Header template. This is done by setting the root attribute of a ClinicalDocument/templateId element to the value 2.16.840.1.113883.10.20.22.1.1.

As explained in The templateId element, it is permissible to have multiple templateId elements alongside each other. In fact, this is very commonly the case with C-CDA documents in the CDA Header – as both conformance to the US Realm Header template as well as conformance to one of the C-CDA document templates is asserted.

For example, the CDA Header for a C-CDA Continuity of Care (CCD) document, has these lines in its header:

<ClinicalDocument ...>
   ...
   <templateId root="2.16.840.1.113883.10.20.22.1.1"/>
   <templateId root="2.16.840.1.113883.10.20.22.1.2"/>
   ...

In this example, the first templateId element asserts conformance to the C-CDA US Realm Header template and the second asserts conformance to the C-CDA CCD document template (note that the order of the templateId elements is not important).

MU2 Requires Only Conformance to the US Realm Header Template
As noted, every C-CDA document that asserts conformance to a C-CDA document template, also asserts conformance to the US Realm Header template.

When it comes to Meaningful Use (MU) C-CDA documents, the MU2 guidelines state that the use of a specific C-CDA document template is allowed, but not required. The only document-level template requirement for MU2 C-CDA documents is the US Realm Header.

Thus, a C-CDA document is valid for use with MU2 even if it has only one ClinicalDocument/templateId element, provided the value assigned to its root attribute is: 2.16.840.1.113883.10.20.22.1.1.

Refer to Does MU2 define C-CDA document templates?, for additional information about C-CDA template requirements in MU2.

US Realm Header Template Requirements
The article What does the CDA Header contain?, overviews the contents of the CDA Header. The C-CDA US Realm Header template addresses most of the top-level elements that can potentially be part of a CDA Header, as presented in that article.

A series of CDA PRO Know articles is being prepared to review each part of the CDA Header as per the requirements of the C-CDA US Realm header.

Other CDA PRO Know Articles Referenced In This Article