Half of all childhood asthma cases are 'overdiagnosed'

"Half a million children who have been diagnosed with asthma may not actually have the condition," The Daily Telegraph reports. That is the finding of a new study that, while carried out in the Netherlands, is likely to have implications for the UK.

The study used a spirometer (a device that can measure lung function), and in some cases, additional allergy tests, on around 650 children who had been previously diagnosed with asthma.

The researchers found that around half (53.5%) of children aged 6 to 17 years diagnosed with asthma probably didn’t have the condition after all. This means they could be taking asthma drugs they don’t need, needlessly exposing them to potential side-effects.

The cause of the problem, they say, is that GPs are not using some of the recommended lung function tests to confirm an asthma diagnosis in children over the age of six. Instead, they are relying mainly on a history of symptoms like coughing and wheezing.

For example, only 16.1% of the 652 children diagnosed with asthma in the Dutch study had a spirometry test.

It is important to recognise that these results may not represent the situation in England. That said, as it is such a common condition, there are no set English guidelines for diagnosis of childhood asthma, and it is likely that many diagnoses are made on symptom history alone.

The health watchdog for England and Wales, NICE, is aware of this potential issue and is currently reviewing its guidance to improve asthma diagnosis. A previous draft of this guidance recommended that spirometry should be used as the first-line investigation for diagnosing asthma in children over the age of and adults.

Where did the story come from?

The study was carried out by researchers from Julius Health Care Centers and University Medical Center Utrecht from the Netherlands, which received no specific funding for this study.

The study was published in the peer-reviewed British Journal of General Practice.

The UK’s media reporting was generally accurately, but failed to make it clear that this study took place in the Netherlands and not the UK. Assuming that the Dutch overdiagnosis estimate (53.5%) would be the same in the UK is guesswork, and needs proper investigation.

The Telegraph usefully explained what the medicines regulator in England and Wales, NICE, was planning in terms of asthma guidelines. Professor Mark Baker, director of clinical practice at NICE, was quoted as saying: "NICE is currently developing a guideline to provide advice for primary, secondary and community care healthcare professionals on the most suitable tests for accurately diagnosing asthma, and how to help people monitor and control their symptoms."

What kind of research was this?

This was a retrospective study looking at the medical records of children aged 6 to 17 diagnosed with asthma in the Netherlands.

As the researchers say, asthma is one of the most commonly diagnosed diseases in childhood. It has been reported that 1 in every 11 children in the UK has asthma. Referencing Dutch, US and UK guidelines, they say how a combination of symptoms, examination findings and lung function tests are needed to form the diagnosis. In those aged under 6, lung function tests can’t be performed, so diagnosis has to be symptom-based.

This study is a potentially accurate way of establishing what happened in the run up to their diagnosis, but relies heavily on the accuracy and completeness of the medical records.

What did the research involve?

The research team looked at the medical records of 652 children aged 6 to 18 years, who had received a diagnosis of asthma or used an inhaler most of the year. This didn’t include children who used an inhaler for just the winter months.

They trawled through the records to see what lung function tests, if any, had been recorded leading up to the diagnosis, as well as any drugs they had been prescribed.

Correct or probable asthma diagnosis was defined in line with a handful of international guidance documents. Confirmed asthma was defined as recurrent shortness of breath or wheezing, which was demonstrated to be reversible on lung function tests (such as spirometry) after giving an inhaler to dilate the airways. The diagnosis may also have been supplemented by allergy tests. Probable asthma, meanwhile, included those with symptoms and examination findings that were suggestive of asthma – but without the spirometry testing.

The same guidance was used to define those with unlikely or no asthma, which were combined to create an "overdiagnosed" group.

The team also looked at children under six who were diagnosed based on symptoms (which is appropriate at this age) but who were not reviewed afterwards to confirm the diagnosis with other tests, which is another unique source of overdiagnosis.

What were the basic results?

Of the 652 children diagnosed with asthma or treated for it:

• 105 children (16.1%) were confirmed by spirometry, so were deemed correctly and accurately diagnosed
• 151 (23.2%) had probable asthma, but needed spirometry to confirm it for sure
• 349 (53.5%) were deemed as overdiagnosed; the vast majority (344) had unlikely asthma and five had their asthma diagnosis ruled out after having a spirometry test
• 47 (7.2%) were probably not asthmatic, and had not been given an asthma diagnostic code, so were not classed as overdiagnosed in this study; they had, presumably, been prescribed an inhaler, otherwise they wouldn’t have been included in the study

How did the researchers interpret the results?

The researchers concluded that: "overdiagnosis of asthma was found in more than half of the children, leading to unnecessary treatment, disease burden, and impact on their quality of life.

"Only in a few children was the diagnosis of asthma confirmed using lung function tests, despite this being recommended in international guidelines."

Conclusion

This study suggests that around half of children aged 6 to 17 in the Netherlands diagnosed with asthma, or using an inhaler year-round to treat it, don’t actually have asthma. 

The media headlines say the same is happening in the UK, but the study provides no direct evidence to support this. We should not be complacent, though. The situation in the UK could be the same, or even worse, so needs proper investigation.

The Netherlands may have specific issues leading to more or less overdiagnosis compared to the UK. For example, the study authors say, lung function tests on children are not often performed in the Netherlands, because patients have to be referred to a hospital for the tests. This may cause an extra barrier to an asthma diagnosis. In the UK, many GPs are also likely to initially give a working diagnosis based on symptoms and examination findings, and may give a trial of asthma treatment to see if children respond. Hand-held peak flow meters are regularly available in general practice, but children may not always be referred to hospital for lung function tests like spirometry as a first step. 

NICE, the health watchdog that sets the guidance to GPs and other doctors on diagnosing asthma in England and Wales, is currently reviewing its advice. The estimated publication date of the new guidance is not stated on their website, so it is unclear whether this study will be part of the evidence it looks at in reaching its new asthma recommendations. Based on previous publication times, we would expect the guidance to be published later this year, or possibly at the beginning of 2017.

If you are concerned about your own, or your child’s, asthma diagnosis, then contact your GP. Do not stop treatment with asthma drugs prescribed to you, or your child, without speaking to a doctor, as this could be dangerous.