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As a chronic disease with no cure, asthma can affect patients in many ways. Symptoms such as coughing, wheezing, shortness of breath and chest tightness can all prevent patients from taking part in certain activities.1 Asthma is also the second most common reason for hospitalisation in children and the fourth most common reason in adults.2 What’s more, increases in asthma exacerbations have been linked to psychiatric disorders, such as depression.1
Asthma exacerbations are commonly known as asthma attacks or flare-ups. They can be described as a worsening in symptoms and lung function compared to a patient’s normal condition.1
Exacerbations are often a reaction to external factors, for example pollen or pollution. They can also be a result of poor medication adherence. The frequency and severity of exacerbations vary a great deal from patient to patient, and severe exacerbations can even occur in those with mild or well-controlled asthma.1
NIOX VERO testing a Child’s FeNO with Mother and Doctor present.
Preventing exacerbations is a vital part of asthma control. It is important that patients have access to relevant information and training, for example in how to use their inhaler.
Traditional asthma management consists of a mix of subjective and objective measures. Subjective measures include clinical history, symptom diaries and quality of life questionnaires. Examples of objective methods are peak flow and spirometry tests.Even though asthma may seem under control, patients may still experience exacerbations.1
The Seasonal Asthma Exacerbation Predictive Index (saEPI) has identified eight variables as risk factors for asthma exacerbations, including age, allergic propensity, blood eosinophils, an exacerbation in the previous season, fractional exhaled Nitric Oxide (FeNO) level and ICS dosage.3
In the early 1990s, researchers discovered that human lungs produce Nitric Oxide (NO). A couple of years later, they found a connection between airway inflammation and the amount of NO in exhaled breath – asthma patients tend to have higher levels of NO.4
Whereas traditional lung function testing and spirometry measure airflow, FeNO testing measures airway inflammation. This is really useful additional information because asthma comprises both airway inflammation and airflow limitation.1 In addition, poor airflow and obstructed airways are not always related to asthma as there may be other causes of airflow limitation.5
A FeNO value of <25 parts per billion (ppb) is considered low and indicates a lower likelihood of airway inflammation. A FeNO value of >50 ppb is considered high and indicates that airway inflammation is likely.5 A FeNO level above 50 ppb is a significant risk factor for uncontrolled asthma whilst FeNO ≥ 25 ppb is a strong predictor of asthma exacerbations.6,7
Several recent studies have shown that adjusting treatment based on regular FeNO testing helps to reduce the number of exacerbations significantly. The most comprehensive summary, published by Petsky et al. in 20188, concluded that exacerbations can be reduced by as much as 40-50% with FeNO-guided asthma management.6
It is important to be aware that several factors could influence a person’s FeNO score, including age, allergen exposure, smoking habits and certain foods (such as those rich in nitrate). It is therefore recommended to monitor an individual’s FeNO levels over time and be alert to any changes that could indicate the risk of an exacerbation. The American Thoracic Society (ATS) suggests that an increase greater than 20% for values over 50 ppb or more than 10 ppb for values lower than 50 ppb between visits can be considered a significant increase.5
Learn more about the gold standard FeNO device.
1. Global Initiative for Asthma (GINA). Global strategy for asthma management and prevention. 2021 update.
2. Meltzer EO 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. Hoch HE et al. Can we predict fall asthma exacerbations? Validation of the seasonal asthma exacerbation index. J Allergy Clin Immunol. 2017;140(4):1130-7.
4. Yates DH et al. Effect of a nitric oxide synthase inhibitor and a glucocorticosteroid on exhaled nitric oxide. Am J Respir Crit Care Med. 1995;152(3):892-6.
5. Dweik RA et al. An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FeNO) for clinical applications. Am J Respir Crit Care Med. 2011;184(5):602-15.
6. Malinovschi A, Janson C, Borres M, Alving K. Simultaneously increased fraction of exhaled nitric oxide levels and blood eosinophil counts relate to increased asthma morbidity. J Allergy Clin Immunol. 2016;138(5):1301-8.e2.
7. Mansur AH et al. Disconnect of type 2 biomarkers in severe asthma; dominated by FeNO as a predictor of exacerbations and periostin as predictor of reduced lung function. Respir Med. 2018;143:31-38.
8. 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.