CaBIG Flavors of Null
caBIG Flavors of Null
Some of the code sets being considered by the caBIG VCDE working group included concept codes that didn't fit the same category as the rest of the codes. As an example, the Sex/Gender Candidate Data Standard included the code Unknown, which meant "unknown, not observed, not recorded, or refused". Rather than being a possible value representing gender, Unknown really represented a bit of metadata that:
- indicated that a "meaningful" code was not present
- gave a fairly generic reason why the code wasn't there
Among the disadvantages of the approach above:
- software has to be specialized to recognize the absence of information on an element-by-element basis - Unknown in gender, perhaps NA in second data element, UNK in a third.
- this approach only works with coded fields. How should some represent the fact that an address is missing because they didn't ask for it? How would they differentiate this from a missing address because the patient refused to supply it?
This gives rise to a more general question - should this type of metadata be included in individual code sets at all, or should it be generalized in a way that it could apply to any data element? The focus of the "Flavors of Null" working group is to address the following questions:
- Should the fact that information is not supplied and the reason for its absence be treated differently from other types of information?
- If so, how should such information be treated?
Health Level Seven (HL7) has developed a possible approach and solution to this issues. The Version 3 Data Type Specification puts