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Managing asthma with FeNO testing to improve patient outcomes

Asthma is characterised by chronic airway inflammation. It is one of the main causes of the exacerbations – or asthma attacks – that can have such a debilitating impact on patients' lives. This article looks at fractional exhaled nitric oxide (FeNO) and how monitoring their FeNO levels can reduce the impact asthma has on patients’ quality of life.

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The Global Initiative for Asthma (GINA) describes the goals of asthma management as risk reduction and symptom control, with the aim of relieving the burden on the patient. Risks include exacerbations, airway remodelling, the side-effects of medication and asthma-related death.1 Reducing exacerbations is the top priority, with asthma the second most common reason for hospitalisation in children and the fourth most common reason in adults.2 Asthma therefore comes at a huge societal cost in missed school and work, not to mention the drain on the healthcare economy.1

GINA 2022 points out that even patients who exhibit relatively few asthma symptoms may still be at increased risk of exacerbation and physicians should look out for potentially modifiable risk factors. These modifiable risks come not only in the form of medication, co-morbidities and environmental exposures, but also lung function and of course Type 2 airway inflammation, which is identifiable through elevated FeNO testing.1 High FeNO values are associated with a greater risk for asthma exacerbations but FeNO-guided asthma management has been shown to reduce their occurrence by up to 50%.3,4

Personalised treatment

According to GINA, ongoing treatment decisions should be based on a personalised cycle of assessment, adjustment and review. Controller medication can be titrated in a stepwise approach to achieve good symptom control, for example. Continual assessment should then help with control as part of asthma management.

FeNO can help in both adult and paediatric care. In 2018, Petsky et al published a systematic review and meta-analysis looking at tailoring asthma treatment on inflammatory biomarkers, including FeNO testing.4 Sixteen randomised controlled trials were included, with 2,284 participants over six to 12 months. The number of participants with exacerbations was significantly lower in the FeNO group vs control. The authors calculated the numbers needed to treat to benefit, which was 12 in adults and nine in children, confirming FeNO-guided management is very efficient at reducing exacerbations.

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Studies have also shown that performing FeNO testing enabled physicians to confidently update treatment titration in up to a third of patients. An observational study, carried out by Hanania in 2018, involved 337 respiratory specialists and 7,901 asthma patients.5 The clinicians made an initial assessment and kept track of their asthma treatment plans before and after FeNO testing. Their records showed that after FeNO measurement, changes were made to the treatment plan in 31% of cases, and prescriptions for corticosteroids were adjusted in 90% of those cases. The study concluded that FeNO monitoring can help identify patients with high levels of airway inflammation not diagnosed with usual care so clinicians can adjust therapy to potentially avoid future exacerbations.

Once asthma is controlled, regular FeNO monitoring will highlight any future loss of control and predict asthma relapse.6 Up to 80% of patients are not adherent to their controller medication, for example, which may lead to a loss of control of airway inflammation and, again, increased risk of exacerbation. Non-adherence can occur through missed doses or incorrect inhaler technique, with FeNO levels usually higher in non-adherent patients. FeNO monitoring also allows physicians to limit the use of high-dose inhaled corticosteroids and avoid the long-term consequences of steroid intake.7 Many studies have looked at how FeNO testing can be used to uncover non-adherence. One of the most recent, published by Heaney et al in 2019, showed that FeNO levels reduce by up to 50% in four days when patients take their medication as prescribed.8

FeNO testing takes less than two minutes to perform and see the results at the point-of-care. The process is safe, easy and non-invasive with a handheld device such as NIOX VERO®, in patients from the age of four generally and seven in the US.

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1. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. 2022 update.
2. Meltzer et al. Asthma burden in the United States: results of the 2009 Asthma Insight and Management survey. Allergy Asthma Proc. 2012;33(1):36-46.
3. Busse WW et al. Baseline FeNO as a prognostic biomarker for subsequent severe asthma exacerbations in patients with uncontrolled, moderate-to-severe asthma receiving placebo in the LIBERTY ASTHMA QUEST study: a post-hoc analysis. Lancet Respir Med. 2021;9(10):1165-1173.
4. Petsky HL et al. Tailoring asthma treatment on eosinophilic markers (exhaled nitric oxide or sputum eosinophils): a systematic review and meta-analysis. Thorax. 2018;73(12):1110-9.
5. Hanania NA et al. Measurement of fractional exhaled nitric oxide in real-world clinical practice alters asthma treatment decisions. Ann Allergy Asthma Immunol. 2018;120(4):414-418.
6. Wang K et al. Using fractional exhaled nitric oxide to guide step-down treatment decisions in patients with asthma: a systematic review and individual patient data meta-analysis. Eur Respir J. 2020;55(5):1902150.
7. Smith AD et al. Use of exhaled nitric oxide measurements to guide treatment in chronic asthma. N Engl J Med. 2005;352(21):2163-73.
8. Heaney LG et al. Medical Research Council UK Refractory Asthma Stratification Programme (RASP-UK). Remotely monitored therapy and nitric oxide suppression identifies nonadherence in severe asthma. Am J Respir Crit Care Med. 2019;199(4):454-464.