A recent Daily Telegraph headline really annoyed me: it stated that 50% of children with asthma have been incorrectly diagnosed. This was irresponsible journalism in my opinion, seeking to undermine GPs and create a sensational headline resulting in widespread TV coverage which alarmed many people with asthma. This was based on a Dutch research paper which based asthma diagnosis on spirometry.
There is no specific test for diagnosing asthma
There is no specific test for diagnosing asthma. It is diagnosed on clinical grounds based on a history of intermittent respiratory symptoms, a response to anti-asthma treatment and demonstration of variable airflow obstruction in the lungs. Acceptable tests of airflow obstruction include spirometry (which requires calibrated equipment, technical expertise and considerable co-operation by the patient) and peak expiratory flow (PEF) which can be adequately performed by most children over the age of five years. Peak flow meters are cheap, reliable and available in the NHS. The only proviso regarding PEF is that ideally patients should have their own meter, because meters may vary from one to another according to the standard set for manufacturers.
This is because asthma is a disease that fluctuates by definition – symptoms come and go, and lung function varies from time to time. Someone with asthma may be able to perform at an international competitive sports event one day, and on another, suffer a life threatening attack. Someone with intermittent respiratory symptoms, relieved by bronchodilator therapy, who performs normal spirometry in the surgery or hospital clinic, may still have asthma.
Sometimes repeated lung function tests are needed, possibly before and after bronchodilator treatment to make or exclude a diagnosis of variable airflow obstruction.
I am convinced that we can do better regarding asthma diagnosis and treatment in the UK, but I disagree with those who suggest that GPs must or should use spirometry as a first line test to diagnose asthma. While I do have a potential conflict of interest as one of the authors, the Global Initiative for Asthma, GINA, guide (which is more pragmatic than UK guidelines and written for busy GPs) includes serial PEF as one of the evidence based methods for diagnosing asthma.
In my own practice, I use serial PEF diaries both to diagnose asthma and as part of a personalised self-management plan. When I first suspect asthma, or if I change medication, I provide patients with a PEF meter and a chart which facilitates the process of diagnosis at the follow up review. Furthermore, this helps the patient or parent understand how the medication works, and provides very good information on when to worry. 45% of those who died from asthma in 2012 failed to call for or obtain medical assistance; not surprisingly, because 77% had no evidence of ever being provided with a personalised asthma action plan (PAAP). In my view, PEF diaries are a very useful adjunct to a PAAP particularly in managing an asthma attack.
Saying that GPs should just rely on spirometry will lead to underdiagnosis, a far greater danger than the overdiagnosis that the Telegraph article warns of.
Dr Mark Levy FRCGP is a GP in London, Respiratory Lead at Harrow CCG and executive board member of GINA.