The case against a negationInd extension for supply and encounter in CDA and QRDA

It's been proposed recently that the prohibition in CDA Release 2.0 against extensions altering the semantics of the information doesn't apply to RIM based extensions.  What the standard has to say in section 1.4 on Extensibility is [emphasis mine]:

Locally-defined markup may be used when local semantics have no corresponding representation in the CDA specification. CDA seeks to standardize the highest level of shared meaning while providing a clean and standard mechanism for tagging meaning that is not shared. In order to support local extensibility requirements, it is permitted to include additional XML elements and attributes that are not included in the CDA schema. These extensions should not change the meaning of any of the standard data items, and receivers must be able to safely ignore these elements. Document recipients must be able to faithfully render the CDA document while ignoring extensions.

The rationale for including this extension in QRDA is to enable one measure (of 93) to be able to report that something was not supplied to the patient.

We did a risk analysis of this today on a special Structured Documents call.  Here's the scenario:

Data is captured for quality reporting and quality improvement activities.
Within that context, rules are created to ensure that patients are followed up on if they aren't getting appropriate treatment as evidenced by supply records.

1. A patient with DVT risk is ordered prophylaxis.
2. However, that prophylaxis is not supplied for some reason (e.g., patient couldn't afford to pay).
3. This is recorded using the extension.
4. A system that uses the proposed extension will correctly detect that the supply did not occur, and can initiate followup.  However, a system that does not use the proposed extension and is developed with the understanding that unrecognized extensions can safely be ignored will not recognize that the supply did not occur.  In fact, it will instead recognize the opposite, that supply did occur.
5. As a result of this, no followup on the necessary intervention is performed.  
6. Due to the resulting delay to detect that the prophylaxis was not given, a life threatening health event occurs.

We need to assess three things:

1. The severity of harm, which we evaluated as critical/life threatening [different organizations may use different terms].
2. Probability of occurrence of the hazard: Care management systems today are looking for the absence of the supply signal.  Presenting a supply signal using QRDA with the extension will always cause this trigger to fail.  Due to the way it interferes with followup activities, is unlikely to be noticed by a provider, so the probability of occurrence is high that it will occur.
3. Likelyhood of harm: This would have to be ratedMechanical prophylaxis can reduce the risk of DVT from 27% to 13% alone, or when used with medications, from 15% to 2% [see http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1925160/].

If you work out the rest, you realize this is not really a workable solution by itself.  Something else has to be done.  Documenting the extension and putting some clear warnings around it is something we know doesn't work well.  Trying to create patient safety in a design through labeling is the least effective method according to the FDA.

If I were the product manager for the 93 quality measures, I'd pull the one in question and release it later when CDA Release 2.1 (or as seems more likely, CDA on FHIR) has the capacity to address the need.