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A PCRS Consensus: FeNO testing for asthma diagnosis

The fractional exhaled nitric oxide (FeNO) test measures the level of NO in the exhaled breath and provides an indication of eosinophilic inflammation in the lungs. 

Alongside a detailed clinical history and other important tests to assess variability (peak flow, reversibility and challenge tests) it is used to support the diagnosis of asthma. PCRS has produced this consensus position on the use of FeNO in primary care to support the diagnosis of asthma.

The article reviews the NICE and BTS/SIGN clinical guideline recommendations on the issue. It also explores the benefits, limitations and challenges of using this test in the primary care setting.

The article concludes that:

  • FeNO testing is a quantitative, non-invasive, simple and safe test making it suitable for use in the primary care setting when conducted by an appropriately trained health care professional competent to deliver and interpret the results. 
  • The benefits of FeNO testing in primary care are:
  • Patients don’t have to be referred to secondary care for additional testing. 
  • A positive FeNO test when considered alongside respiratory symptoms and lung function tests suggestive of asthma, supports a diagnosis.
  • But there are concerns about the necessity for FeNO testing in primary care for every asthma diagnosis and about its cost-effectiveness.  It may be more appropriate for FeNO testing to be carried out in diagnostic centres in the community, intermediate or secondary care setting.
  • Given the limitations of extending FeNO testing to all patients presenting with symptoms suggestive of asthma, the current PCRS position aligns with the guidance issued by BTS/SIGN. This is that the FeNO test should be used as an optional investigation to test for eosinophilic inflammation when there is diagnostic uncertainty.