Friday, May 18, 2007

Adverse Events are Not Observations

A further HL7-relevant issue discussed at the recent Clinical Trial Ontology workshop concerned the peculiar HL7 practice of identifying events (for example events of drug interaction) with their observations. This practice is, gratifyingly, less pervasive in the BRIDG model of protocol-driven clinical research than in HL7, but it raises its head even there, for example in the identification of adverse events as adverse event assessments at:

CTOM (imported package)::AdverseEvent
Type: Class Extends: Assessment.
Status: Proposed. Version 1.0. Phase 1.0.
Package: CTOM (imported package)
Details: Created on 1/5/2005 11:17:58 PM. Modified on 9/26/2005 2:22:53 PM.

in BRIDG Model Version 1.41.

The issue raised at the Bethesda workshop was: why does HL7 persist in instituting what, on the face of it, is an obviously false assertion, as a central pillar of its information model?

This question becomes all the more important given that, increasingly, the task of adverse event assessment will occur at geographical sites remote from the adverse events themselves -- something which is logically impossible where adverse events are identified with their own assessments. How, on the basis of such an identification could we track shortfalls (for example in hospital practices or equipment) leading to adverse events in the hospitals themselves in such a way as to distinguish them from shortfalls in practices or equipment leading to poor assessments at remote assessor sites?

Perhaps the ever resourceful ingenuity of HL7's coders can find some complex coding procedure to keep these things apart even after having already identified them; but why not keep them apart from the very start, as simplicity and realism (and learnability and economy and patient safety) would suggest?

Two answers present themselves:

1. that we have here yet one more example of the influence on early HL7 of the focus on healthcare billing -- adverse events themselves, unlike observations and assessments, cannot be billed.

2. that HL7 RIM (and to this degree also HL7 tout court) is an information model -- so that 'adverse event' means: 'information about an adverse event', 'adverse event assessment' means 'information about an adverse event assessment', and so on.

But answer 1. seems not to be in keeping with HL7's current, and much more ambitious, goals. And answer 2. does not, in fact, support the given identification, since even on this meta-level, information about an adverse event and information about adverse event assessments remain distinct, and the former is not a subtype of the latter.

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