Tuesday, 15 December 2015

How is your wheezer wired? Asthma vs Viral wheeze in the under 5 year old.

This week, I was asked a very good question by one of my colleagues in primary care: Why are children under the age of five who have recurrent wheeze and who are clearly atopic not given a diagnosis of asthma?  It's a question I have been asked many times before before, often accompanied by a frustrated and confused expression.

Are paediatricians allergic to diagnosing asthma in under five year olds?  It might seem like it.  The answer is no, but the diagnosis is avoided by most paediatricians and some have stopped using that term altogether (preferring multi-trigger wheeze for the under five year olds).  So when is it asthma?

Some children under the age of five with atopy and wheeze are asthmatic (or have multi-trigger wheeze if you like) but most are not.  Most have recurrent viral wheezing.  The difference is all in the circuitry. Remember circuit diagrams?  You may have intentionally blocked them out from your memory but for the purposes of this explanation it will be helpful, especially for the visual/ special learners, of which I am one. 

The thing is that lots of children have viral wheezing episodes and lots of children have atopy, usually in the form of eczema.  To find them both in the same child is reasonably common so association does not prove causation.  For that you need to establish whether the two things are happening in series or parallel.  This is where my circuit diagrams come in.

Fig 1. When a child has episodes of wheeze that are not related to anything other than viral illnesses, then any co-existing atopy is not thought to be part of the problem.  In these cases the diagnosis remains recurrent viral wheeze.

Fig 2. If there are episodes of wheeze that are unrelated to viral illnesses then coexisting atopy is the likely cause and these children are diagnosed with asthma.

Why does it matter what label we give this?  The main reason is that the chronic treatment is different.  In a review article in the BMJ, the evidence is summarised for treating acute episodes of viral wheeze with bronchodilators only, without either acute or prophylactic steroids.
When it comes to knowing whether your patient’s wheeze and atopy are wired in series or parallel, it all comes down to precipitants and interval symptoms.  If the precipitant is always a viral illness and there are no interval symptoms, then the wiring is in parallel (recurrent viral wheeze).  If there are episodes in the absence of viral illness, or there are interval symptoms (usually frequent cough or wheeze) then the wiring is in parallel (asthma).

Are there any drawbacks to having this separate diagnosis?  I can think of a few.  Firstly, having seen life-threatening exacerbations of viral wheeze I know that the acute episodes are just as capable as asthma attacks of becoming severe and deteriorating rapidly.  Recurrent viral wheeze is not a benign condition and children do die from it.

My next concern is whether or not these children get themselves into the system properly in primary care.  I know that with the current systems in place, children with asthma will be easily identified in a General Practice setting and thus get an annual review, inhaler technique checked and an invitation for an annual influenza vaccination.  Children with recurrent viral wheezing should probably also get these, but there is little guidance and no quality framework for recurrent viral wheezing. 

So how do we make sure that these children are managed appropriately?  The separate label of viral wheezing allows us to treat them consistently without giving treatments that are not going to help.  The same label risks putting these children on one side or implying that they are not at risk of severe episodes.
It does however make me wonder if the label of 'multi-trigger wheeze' is a step too far.  The European Respiratory Society Task Force defines a clinical entity "as a cluster of associated features that are useful in some way, such as in managing the child or understanding the mechanisms of disease."  Since the majority of these children are managed by general practitioners I would argue that the diagnosis of multi-trigger wheeze should be useful to them.  I am struggling to see a clear benefit.  Having labels that change and multiply can have a detrimental effect by confusing clinicians and parents alike.  In the pursuit of purism, we can end up with nomenclature which is more academic than practical.

So, let's stick with the terms recurrent viral wheeze and asthma for now.  That still leaves us with the need to ensure that the recurrent viral wheezers get treated as children with a debilitating and potentially dangerous respiratory problem.  So, can General Practitioners come up with solutions to this?  Part of the answer will be awareness and I hope that this little update has helped.  I suspect there is also a need for coding ingenuity.  It may be that others have recognised this conundrum and come up with novel solutions.  If so, please comment below and share your ideas.

Edward Snelson
Medical polyglot
@sailordoctor

Disclaimer: I fear change

References
  1. Andrew Bush, Managing wheeze in preschool children BMJ 2014; 348 
  2. Brand PL et al. Definition, assessment and treatment of wheezing disorders in preschool children: an evidence-based approach. Eur Respir J2008;32:1096-110




2 comments:

  1. Hi Edward, love the website & your trademark orange boxes!

    This is a particularly pertinent question!

    The ERSJ (esp lead author P.Brand) reconsidered the model of MTW vs EVW in - I think - 2014 (reference below), after it didn’t hold up in retrospective studies, with patients moving between groups (?bidirectionally). Brand et al. suggest long-term management on the basis of severity & frequency.

    We actually discussed this labelling system and an approach to the emergent management of "preschool wheeze" in a recent EMA article, also linked below, although it's less focussed on the outpatient management of same.


    Brand PL, Caudri D, Eber E et al.Classification and pharmacological treatment of preschool wheezing:changes since 2008. Eur. Respir. J.2014; 43: 1172–7. http://www.ncbi.nlm.nih.gov/pubmed/24525447

    DFTB in EMA - Easing the Wheeze : http://onlinelibrary.wiley.com/doi/10.1111/1742-6723.12463/epdf

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    1. Thanks Henry. This topic of labelling is one that creates much discussion. It is always helpful when experienced clinicians acknowledge the grey areas.

      I have to reciprocate by admitting my fandom of 'don't forget the bubbles'. Good work. I hope you find the next GPpaedsTips adds value to this discussion.

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