Medical practice

Is asthma being overdiagnosed?

A potentially alarming figure that emerged in the UK news last week was that “1 million” UK adults may have been wrongly diagnosed with asthma – a claim reported in various forms by BBC News, The Guardian, The Daily Telegraph, the Daily Mirror and the Mail Online. 

The headlines followed the publication of new draft guideline (PDF, 670kb) from the National Institute for Health and Care Excellence (NICE) on the diagnosis and management of asthma. Most of the media articles were true to the facts and explained that the guideline was aiming to improve asthma care by improving the accuracy of diagnosis.

So, where did the figure of 1 million come from? All the UK press rallied round a statement in the draft guideline that said: “studies of adults diagnosed with asthma suggest that up to 30% do not have clear evidence of asthma”. What followed was clearly a “back of the envelope” calculation extrapolating this to the number of people receiving treatment for asthma in the UK, which is around 4.1 million. This gave the magic figure of 1.23 million potentially misdiagnosed people.

Unfortunately, the 30% figure in the draft guideline is not referenced, so we can’t find out how accurate it is. We also don’t know whether it applies to specific asthma subgroups, such as those of a specific age, or the severity of a person's symptoms. This makes it difficult to assess whether this calculation is accurate, or even reasonable.

The charity Asthma UK responded in a blog post, saying: “While we welcome the NICE guideline in the hope that it will help people with asthma to receive more personalised care, we are concerned that today’s headlines may make people think twice about taking their asthma medicines”.

“Although it is true that some people may receive treatment for asthma when they currently don’t have symptoms, this does not necessarily mean that they don’t have asthma. So it is vital that everyone diagnosed with asthma keeps taking their medication as prescribed and attends their annual asthma review”.

You should never stop taking any prescribed medication without first consulting with your GP or the doctor in charge of your care. This includes asthma medication.

What is the basis for these current reports?

NICE recently released a draft guideline to improve asthma diagnosis and monitoring.

The draft guideline – NICE's first on asthma – is now open for consultation until March 11 2015, so people and institutions can comment on its initial recommendations. The feedback and comments will be collated and incorporated into revised recommendations. Once agreed, these will form official NICE guidelines, which are expected to guide standard healthcare practice across the UK.

The draft guideline covers the diagnosis and monitoring of asthma in adults, children and young people. It draws on the best evidence available to determine the most clinical and cost-effective way to diagnose people with asthma and determine the most effective monitoring strategy to ensure optimum asthma control.

What does it say?

The draft guideline outlines that there is currently no gold standard test available to diagnose asthma. At the moment, it is mainly based on a thorough history of symptoms taken by an experienced clinician.

However, the guideline stresses that to achieve a more accurate diagnosis, clinical tests should be used alongside symptom assessment. The process the healthcare professional should follow in the initial assessment, and the tests to use, are presented in simple flow charts.

This involves using a combination of tests, depending on the age of the person being assessed. Most commonly this will involve a test called spirometry, to test lung function. This will sometimes be repeated after a person has been given inhaled treatment to dilate the airways – known as a bronchodilator reversibility test. Other tests that may be used include measuring fractional exhaled nitric oxide, as a sign of airway inflammation, and looking at whether the airways are over-responsive to inhaled substances, such as histamine or methacholine. 

The guidance also says that around one in 10 adults with asthma develop the condition because they are exposed to certain substances, such as chemicals or dust, in their workplace. Therefore, the draft guideline now recommends that healthcare professionals ask employed people how their symptoms are affected by work, to check if they may have occupational asthma.

How does the guideline affect you?

If you have asthma, do not change your medication without first consulting a doctor. This could be dangerous, as untreated asthma can be fatal.

If you have concerns that you have been misdiagnosed or are taking medicines unnecessarily, the first thing to do is speak with your health professional.

At present, these guidelines are in a draft form, so may be revised based on feedback and comment over the next few months. In the meantime, there aren’t likely to be changes in the way asthma is diagnosed routinely across the NHS. However, if the changes proposed in this draft make it into the final version, this may lead to a change in practice – most likely, more standardisation around the diagnosis and monitoring of asthma.

The main implications of such a change would be that the accuracy of diagnosing new asthma cases should improve or standardise for people in the UK. The implications for people already diagnosed with asthma are less clear. It could potentially mean that cases where there was uncertainty around the diagnosis would be re-reviewed with further diagnostic tests. This could potentially lead them to be declared asthma-free, or to a change in their medications, as appropriate.

This is a good reminder to take full advantage of your asthma review, which is an appointment with your doctor or asthma nurse to talk about your asthma and discuss how you can better control your symptoms. This is something that everyone with asthma should do at least once a year or more if you have severe asthma symptoms.

NICE says it wants to hear your views. Information on how to comment on the draft guideline can be found here.

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