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European Respiratory Society International Congress 2021 debate: FeNO for the diagnosis of asthma in adults: Friend or foe?
One of the key moments at ERS 2021 came in the form of a friendly and informative debate: FeNO* for the diagnosis of asthma in adults: Friend or foe?1 Dr Iñigo Ojanguren Arranz, from the Respiratory Department of Vall d’Hebron University Hospital in Barcelona, outlined the reasons he considers FeNO a friend. Head of Pneumology and Professor of Respiratory Medicine at the University of Liège, Renaud Louis, gave a rebuttal, asserting his thoughts on why FeNO might be a foe.
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Professor Dr Louis is co-chair of the ERS taskforce on asthma diagnosis while Dr Ojanguren Arranz is one of the group’s core authors. In the process of this taskforce, both have been through a complete review of the literature on nitric oxide.
FeNO as a friend
FeNO advocate Dr Ojanguren Arranz acknowledged that diagnosing asthma can be challenging. Some of the more traditional tools present difficulties, he said. The bronchodilator reversibility test can often produce a false negative result, especially in mild asthma, while bronchial challenge testing facilities are not always available. Testing for FeNO, on the other hand, can be performed quickly, is easy for patients and does not involve excessive cost.
In addition, Dr Ojanguren Arranz noted that FeNO testing in patients with asthma symptoms had been shown by many studies to provide a reliable result with high specificity – up to 90% when FeNO is ≥50 ppb. Couple that with the symptoms, said Dr Ojanguren Arranz, and asthma is very likely.
NIOX VERO testing a Child’s FeNO with Mother and Doctor present.
Dr Ojanguren Arranz pointed to GINA 2021, which states: “Asthma is usually characterised by airway inflammation” – the key trait revealed by FeNO testing. It’s the word “usually” that sets FeNO apart, he said: perhaps airway inflammation is not a feature in every case of asthma – but it is usually – and that’s highly compelling.
Could FeNO be a foe?
Professor Dr Louis then took the floor to convince us that FeNO can be a foe in asthma diagnosis. FeNO can be problematic, he argued, given some asthmatics produce FeNO results in a range that can be found in healthy subjects.
Professor Dr Louis also considered GINA, concerned at the use of the word “usually” when using airway inflammation to characterise asthma. He suggested that, in many cases, the symptom of wheeze was sufficient – and sometimes better than biomarkers. Wheeze, he explained, is caused by airway constriction, one of the defining characteristics of asthma.
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Later, Professor Dr Louis turned his attention to smokers. FeNO levels are dramatically decreased in those who smoke, he said, pointing out that these patients comprise around 20% of the asthmatics generally seen in clinical practice. He noted that new studies would be useful, looking specifically at this group, and indicated that the FeNO evaluations he used had taken this variation into account, reducing FeNO’s effectiveness rating in relation to other diagnostic tests. During his session, Dr Ojanguren Arranz had agreed that, while FeNO results can be modified by infection, smoking and allergy, potentially making asthma difficult to investigate, in non-smokers – who form the majority of the presenting population – and with steroid-naïve patients, the simple probability of asthma increases as FeNO goes up.
Summing up
In conclusion, Dr Ojanguren Arranz remarked that, despite the confounders, when FeNO levels are high and symptoms are present, asthma is likely and healthcare professionals should consider treatment with inhaled corticosteroids (ICS). Professor Dr Louis agreed that FeNO testing was an extremely useful tool to characterise asthma, particularly severe asthma, adding that, after a decade of phenotyping severe asthma because of the availability of biologics, it was probably time to phenotype mild asthma too.
Summing up the debate, co-chair Professor Omar Usmani, from Imperial College, London, concluded that, in the right circumstances, FeNO testing is a friend.
