HL7 CCD: Using different codesystems: please clarify

Question

I am looking at the sample CCD document supplied by HL7 in the CCD implementation guide.

Excerpt:

<title>Results</title>
<text>
    ...
</text>
<entry typeCode="DRIV">
    <organizer classCode="BATTERY" moodCode="EVN">
        <templateId root="2.16.840.1.113883.10.20.1.32"/> <!-- Result organizer template -->
        <code code="43789009" codeSystem="2.16.840.1.113883.6.96" displayName="CBC WO DIFFERENTIAL"/>
        ...
        <component>
            <observation classCode="OBS" moodCode="EVN">
                <templateId root="2.16.840.1.113883.10.20.1.31"/> <!-- Result observation template -->
                <code code="30313-1" codeSystem="2.16.840.1.113883.6.1" displayName="HGB"/>
                ...
            </observation>
        </component>
    </organizer>
</entry>

This is from the lab results section. As far as I know, there is no restriction on what codesystems we can use for identification, is this true? I see that we use 2.16.840.1.113883.6.96 (SNOMED) and 2.16.840.1.113883.6.11 (LOINC), for identifying lab test batteries (groups) and lab tests respectively. Is this done simply to help demonstrate the fact that we can use whichever codesystem we want? Or is there another reason why we do that?

Answer 1

It may depend on what kind of CDA document you are trying to build. There is no hard set rule that you must use LOINC or SNOMED, but those are preferred code systems. Obviously, the more common code systems that people are using, the easier it is to achieve interoperability. Depending on the type of CDA document you are trying to create, there may be rules that code systems are used for capturing certain types of data (eg date of birth should be captured using LOINC). Each document type will have different requirements, but they should have an implementation guide associated with it to help you determine what rules need to be followed.

If you have the need for a custom code system or a different code system, such as HL7 or RxNorm, those should be used in place. Just make sure that the OID filled in the codeSystem attribute matches. If you are using a custom code system, you may want to consider registering it at the HL7 OID site .

If you are still unsure if what you have developed is compliant, I would suggest using the NIST CDA Validation Site . Here, you can drop a sample CDA document, choose your document type and validate it. The generated reports are fairly comprehensive.

Answer 2

If you check the HL7 CCD Implementation Guide, in many places it states something like this:

CONF-398: The value for “Organizer / code” in a result organizer SHOULD be selected from LOINC (codeSystem 2.16.840.1.113883.6.1) or SNOMED CT (codeSystem 2.16.840.1.113883.6.96), and MAY be selected from CPT-4 (codeSystem 2.16.840.1.113883.6.12) or ValueSet 2.16.840.1.113883.1.11.20.16 ResultTypeCode STATIC.

So you have to use one or another.

Answer 3

Just to reinforce @Mike's answer..

The CDA specification generally doesn't specify codesystem bindings, though the CCD implementation guide might (I haven't looked at it). - however if you want interoperability, it's in your interest to use the same code systems (in each field) as your exchange partners. The codesystems used depend on the information that needs to be coded, so can vary. It's unlikely/impossible to use just one codesystem (of those that currently exist) across the whole document.