The unknown substance conundrum…

Is it safe and sensible to record that a patient has had an adverse/allergic reaction to an unknown substance?

This is a question that is causing quite a stir in the HL7 Patient Care email list and I have no doubt that it will be a hot topic in the current FHIR/openEHR Adverse Reaction archetype review. Some are advocating to record a reaction without offering a possible causal substance.

I think we can all agree that it makes absolute sense to record the DIAGNOSIS of an obviously <allergic manifestation> (eg urticaria) to an unknown substance as “<allergic manifestation> of unknown origin”. I think most can comfortably agree with that statement.

Now for the controversial bit…

However while a patient can have a reaction to an unknown substance, I will assert that it does NOT make sense to record an ADVERSE REACTION manifestation to an unidentified substance. I am certainly not denying that a clinician who observes a rash that is clearly of allergic origin, such as an urticaria, will absolutely be thinking in terms of ‘this is clearly of allergic origin and I must investigate further to identify the substance’. This is clearly good clinical practice. However, as clinicians, I am suggesting that sometimes we need to differentiate between what we observe or think from what we might record in a health record at the same given point in time .

In all my years of clinical practice, I cannot remember any paper record where I have ever seen ‘urticaria’ or ‘anaphylaxis’ entered into the Allergy List without a proposed substance being associated. I can see absolutely no reason why we should start doing this for electronic health records.

Both the substance and the manifestation are required to enable a clinician to avoid future exposures in future clinical care. That is the logic behind the existence of the ubiquitous Adverse Reaction or Allergy List.

Until one or more causal substances is postulated and/or confirmed, an isolated clinical manifestation of urticaria or anaphylaxis is, in reality, just a simple (maybe allergy-related) sign, symptom or diagnosis of unknown cause. The act of recording a reaction to ‘nothing’ or ‘unknown substance’ adds no absolutely no value to the Adverse Reaction or Allergy List as it cannot trigger any decision support by a clinical system.

I think I can also safely assert that all clinicians ideally want to be able to prevent a future reaction for their patient, especially in the situation where the substance may not be identifiable at the time of the reaction. This is a key clinical activity that we need to be able to record clearly in EHRs – we cannot afford for an identified allergic reaction to be ‘lost’ in the health record before we can identify the substance.

To that end, the HL7 Patient Care approach has been to record a Reaction Event in the absence of a Substance, while the openEHR approach has been to record the manifestation as part of the health record – symptoms, signs, test results, diagnosis etc, of unknown origin. However for both, a clear imperative is that the clinician can able to flag that this patient has an unresolved puzzle: that there has been a known allergic reaction that may cause future harm if the cause is not identified.

So collectively we need to determine a way for this outstanding health puzzle to be tracked and not lost in the depths of a long ago consultation note. This aligns with the design of Lawrence Weed’s Problem Oriented Medical Records (POMR). In HL7, this approach is captured in their concept of ‘Concern Tracker’, and in the draft Contsys standard (ISO 13940) it is known as a ‘Health Issue Thread’. openEHR needs to develop EVALUATION archetype/s that will support this abstract concepts and support the POMR approach.

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