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Wednesday, August 1, 2012

On dealing with preferred coding in CCDA


This question comes up on the HL7 Structured documents mailing list about this text in CCDA:
If the diagnosis is unknown or the SNOMED code is unknown, @nullFlavor SHOULD be "UNK". If the code is something other than SNOMED, @nullFlavor SHOULD be "OTH" and the other code SHOULD be placed in the translation element (CONF:10142).
The querant wants to know what that means, and provides a few examples (which I've used below). 

If all you have is an ICD-9 (or ICD-10 or other code), and you don't know the SNOMED CT code or cannot map to SNOMED CT, then what you should do is in his example #1 below:

1.  Just provide the ICD-9 code in a translation 
<value xsi:type="CD" nullFlavor="OTH"
    codingSystem="2.16.840.1.113883.6.96">
  <translation code="401.9"
    displayName="Hypertension, essential"
    codeSystem="2.16.840.1.113883.6.104"
    codeSystemName="ICD-9-CM"/>
</value>

But where you have both, or can map from ICD-9-CM and SNOMED CT, then what you should do is in his example #2:

2.  Provide the (mapped) SNOMED CT code up-front, and ICD-9 in translation 
<value xsi:type="CD" code="59621000"
  codeSystem="2.16.840.1.113883.6.96"
  codeSystemName="SNOMED CT"
  displayName="Essential hypertension"/>
  <translation code="401.9"
    displayName="Hypertension, essential"
    codeSystem="2.16.840.1.113883.6.104"
    codeSystemName="ICD-9-CM"/>
</value>

This is exactly the same guidance that I provided in Stage 1 for using the HITSP C32.