Asthma Diagnosis Can FeNO Be Used To Diagnose Asthma? By Pat Bass, MD Pat Bass, MD LinkedIn Twitter Dr. Bass is a board-certified internist, pediatrician, and a Fellow of the American Academy of Pediatrics and the American College of Physicians. Learn about our editorial process Updated on February 17, 2021 Medically reviewed by Daniel More, MD Medically reviewed by Daniel More, MD Daniel More, MD, is a board-certified allergist and clinical immunologist with a background in internal medicine. Learn about our Medical Review Board Print While a large percentage of asthma is due to eosinophilic inflammation, patients whose asthma symptoms are due to other causes of inflammation (e.g. basophils, lymphocytes, or neutrophils) are not likely to benefit from FeNO testing. According to a Clinical Practice Guideline from the American Thoracic Society, FeNO can be used to make a diagnosis of eosinophilic inflammation and support a diagnosis of asthma if objective evidence is needed. More specifically, elevated levels of FeNO indicate inflammation in the lungs and that a patient is likely to respond to inhaled steroids based on previous research. Thus, FeNO more accurately identifies a potential response to treatment rather than making a specific diagnosis of asthma. IAN HOOTON/SPL / Getty Images Problems With Traditional Monitoring Most asthma action plans are currently driven by asthma symptoms or peak flows. Traditional symptoms such as wheezing, chest tightness, cough, and shortness of breath can be very non-specific and are not necessarily related to the amount of inflammation that is actually present in your lungs. Peak flow may only be mildly correlated with the degree of airway inflammation according to some research. Advantages of FeNO for Monitoring Asthma About half of all asthma cases involve eosinophilic airway inflammation. This type of inflammation results from the upregulation of mast cells and other cells that specifically increase nitric oxide levels. As previously stated, patients with eosinophilic inflammation have elevated FeNO levels, while patients with inflammation from other causes do not have elevated FeNO levels. Additionally, studies have demonstrated biopsy-proven inflammation in patients with elevated FeNO levels. As a result, elevated FeNO levels are thought to identify patients who are likely to respond to steroid treatment and studies have shown that elevated FeNO levels are one predictor of a positive response. FeNO Levels FeNO levels are currently measured in healthcare provider offices. Patients exhale completely and then take a normal breath in through a disposable filter. FeNO levels are then available in a few minutes for interpretation by your practitoner. Normal, intermediate, and elevated levels are presented in the table below. Adults Children 12 and older 4–12 Low < 25 < 20 Intermediate ≥ 25- ≤ 50 ≥ 20- ≤ 35 High > 50 >35 *ppb= parts per billion FeNO Use in Asthma Care The Optimum Patient Care Research Data is the United Kingdom's respiratory database that contains anonymous, long-term outcomes data for asthma patients in the UK. The database was examined to identify patients not receiving inhaled steroid therapy but might benefit and patients who were being managed medically using FeNO as a marker. Investigators found that small numbers of primary care physicians treating asthma using FeNO. Interestingly, the use of FeNO assessment was associated with increased adherence to a treatment regimen in addition to its use to initiate inhaled steroid therapy or an indicator for step-up therapy. Additionally, other research has demonstrated the rate of asthma exacerbations to be lower in patients using FeNO as part of their monitoring strategy. A U.S. Based study at 10 asthma centers found that FeNO use led to higher doses of inhaled steroids compared to standard management based on asthma guidelines, but did provide significant improvements in asthma symptoms that were clinically significant. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 0 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Bateman ED, Boushey HA, Bousquet J. Can guideline-defined asthma control Be achieved? The gaining optimal asthma controL study. 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