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How can FeNO help optimise asthma treatment and improve ICS adherence?

Inhaled corticosteroids (ICS) are the cornerstone of asthma controller therapy. However, patients don’t always adhere to their treatment or use good inhaler technique, and ICS doses are not always optimal. In this article we’ll discuss how FeNO (fractional exhaled nitric oxide) testing can help optimise treatment decisions for ICS and check medication adherence.

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Asthma is one of the most common chronic diseases worldwide. Airway inflammation is a central part of the condition and can lead to symptoms such as cough, wheezing, breathlessness and chest tightness.1 The first asthma treatment guidelines from the 1990s focused on treating the inflammation that causes asthma.2 ICS are anti-inflammatory and very effective in reducing airway inflammation.1

Why might patients remain symptomatic despite ICS?

It soon became clear that not all patients labelled as asthmatics responded to ICS as expected.3 A prospective, multicentre cohort study by Aaron et al in 2017 showed that about 33% of asthma diagnoses in adults may be incorrect.4 Some asthma symptoms are common to other diseases, such as chronic obstructive pulmonary disease (COPD) and vocal cord dysfunction, so early and accurate asthma diagnosis is fundamental.5

Nurse FeNO testing female patient with NIOX VERO®

A patient performing a FeNO test with NIOX VERO®

Tools for diagnosing asthma include assessments of personal and family history, physical examination and lung function tests, such as spirometry.1 However, while these are all important tools, they don’t measure airway inflammation. As a result, various international guidelines produced by the American Thoracic Society (ATS), European Respiratory Society (ERS) and the Global Initiative for Asthma (GINA) now recommend measuring a patient’s FeNO levels for an accurate picture of the disease.1,5,6

Asthma patients with a high FeNO level are typically at 2.5 times greater risk of experiencing an exacerbation.7 With this in mind, considering FeNO as a modifiable risk factor and working to decrease a patient’s FeNO score through treatment optimisation will lower that risk.

FeNO can help to optimise therapy

FeNO was discovered in the 1990s as a biomarker in exhaled breath. Soon after, researchers understood that FeNO could help diagnose airway inflammation.5,8 It is now well established that FeNO levels are elevated in asthma and reduced by steroids.5 Thanks to simple and non-invasive testing devices like NIOX VERO®, clinicians can now easily measure FeNO at the point-of-care.

Studies have shown that clinicians who did not test FeNO levels were unable to recognise significant airway inflammation in 50% of patients.9,10 It was also shown that adding FeNO testing resulted in clinicians altering their asthma treatment plan in more than a third of cases.9,10 90% of those cases involved changes to the prescription of ICS.10

Treatment decisions based on regular FeNO testing also resulted in up to 50% fewer exacerbations and fewer hospital admissions, compared to traditional asthma management.11-13 In essence, a FeNO level >50 ppb is considered a significant risk factor for uncontrolled asthma but by monitoring patients through FeNO testing, physicians can spot the issue as quickly as possible.14

FeNO as an indicator for ICS adherence

Non-adherence to preventer medication is a major reason for poor asthma control. Up to 75% of the costs associated with asthma may be due to patients not taking their medication correctly.15

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According to several studies, regular FeNO testing is a useful tool for checking whether patients are complying with their ICS treatment.16-18 FeNO tests can also help determine whether patients have an effective inhaler technique, which can influence the success of treatment. For example, compliance with ICS treatment was closely observed during an asthma camp for children. Improved adherence resulted in a significant reduction in FeNO levels.19

A study conducted by Heaney at al in 2019 showed FeNO levels were significantly reduced in non-adherent patients when daily ICS administration was observed.18 Typically, FeNO levels reduce by half in four days when patients comply with their medication. The researchers recognised that non-adherence with ICS in asthma was common and consistently associated with poor clinical outcomes. They noted that assessment of adherence to ICS is challenging, with physician estimates and patient self-report overestimating adherence when compared with objective measures. However, the study found regular monitoring minimised the risk of committing a patient to unnecessary treatment when their disease could be readily controlled with ICS. The researchers added that using FeNO testing to monitor adherence was straightforward for both the patient and the clinician.

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1. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. 2021 update.
2. National Heart, Lung, and Blood Institute (NHLBI). National Asthma Education and Prevention Program Expert Report: Guidelines for the Diagnosis and Management of Asthma. 1991.
3. Szefler SJ et al. Asthma Clinical Research Network of the National Heart Lung, and Blood Institute. Significant variability in response to inhaled corticosteroids for persistent asthma. J Allergy Clin Immunol. 2002;109(3):410-8.
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