...
This analysis is the only possble view of affairs, but it does ake care of the need to know what the patient or clinician said, even if it was not definitive. Complicated null flavour approaches tend to mix up such situations with the situation where data were unavailable for a techincal reason.
HL7 Approach
1 | NI | no information | The value is exceptional (missing, incomplete, improper). No information as to the reason for being an exceptional value is provided. This is the most general exceptional value. It is also the default exceptional value. |
2 | INV | invalid | The value as represented in the instance is not an element in the constrained value domain of a variable. |
3 | OTH | other | The actual value is not an element in the constrained value domain of a variable. (e.g., concept not provided by required code system). |
4 | NINF | negative infinity | Negative infinity of numbers. |
4 | PINF | positive infinity | Positive infinity of numbers. |
3 | UNC | unencoded | No attempt has been made to encode the information correctly but the raw source information is represented (usually in originalText). |
3 | DER | derived | An actual value may exist, but it must be derived from the provided information (usually an expression is provided directly). |
2 | UNK | unknown | A proper value is applicable, but not known. |
3 | ASKU | asked but unknown | Information was sought but not found (e.g., patient was asked but didn't know) |
4 | NAV | temporarily unavailable | Information is not available at this time but it is expected that it will be available later. |
3 | QS | sufficient quantity | The specific quantity is not known, but is known to be non-zero and is not specified because it makes up the bulk of the material.'Add 10mg of ingredient X, 50mg of ingredient Y, and sufficient quantity of water to 100mL.' The null flavor would be used to express the quantity of water. |
3 | NASK | not asked | This information has not been sought (e.g., patient was not asked) |
3 | TRC | trace | The content is greater than zero, but too small to be quantified. |
2 | MSK | masked | There is information on this item available but it has not been provided by the sender due to security, privacy or other reasons. There may be an alternate mechanism for gaining access to this information.Note: using this null flavor does provide information that may be a breach of confidentiality, even though no detail data is provided. Its primary purpose is for those circumstances where it is necessary to inform the receiver that the information does exist without providing any detail. |
2 | NA | not applicable | No proper value is applicable in this context (e.g., last menstrual period for a male). |
This is the HL7 nullFlavor table as of Dec 2007. (Grahame)
It would seem that some of these are not appropriate in the context of openEHR. I would think that OpenEHR has handled the concepts of OTH, NINF and PINF differently, and needn't support them.
I'd be interested to know how OpenEHR models the concepts of UNC, DER, QS and TRC