Higher than normal levels of exhaled nitric oxide generally mean your airways are inflamed — a sign of asthma.
- Levels under about 20 parts per billion in children and under about 25 parts per billion in adults are considered normal.
- More than 35 parts per billion in children and 50 parts per billion in adults may signal airway inflammation caused by asthma.
Nitric oxide test results can vary widely from person to person. When interpreting test results, your doctor will consider a number of other factors. These may include:
Aug. 20, 2016
- Your asthma signs and symptoms
- Results of other tests, such as peak flow tests or spirometry tests
- Past nitric oxide test results
- Medications you take
- Whether you have a cold or the flu
- Whether you have hay fever or other allergies
- Whether or not you smoke
- Your age
- Dweik RA, et al. An official ATS clinical practice guideline: Interpretation of exhaled nitric oxide levels (FENO) for clinical applications. American Journal of Respiratory and Critical Care Medicine. 2011;184:602.
- Lim KG, et al. The use of fraction of exhaled nitric oxide in pulmonary practice. Chest. 2008;133:1232.
- Deykin A, et al. Exhaled nitric oxide analysis. http://www.uptodate.com/home. Accessed Oct. 14, 2013.
- Silkoff PE, et al. ATS/ERS recommendations for standardized procedures for the online and offline measurement of exhaled lower respiratory nitric oxide and nasal nitric oxide. American Journal of Respiratory and Critical Care Medicine. 2005;171:912.
- Dinakar C. Exhaled nitric oxide in pediatric asthma. Current Allergy and Asthma Reports. 2009;9:30.
- Malinovschi A, et al. Exhaled nitric oxide levels and blood eosinophil counts independently associate with wheeze and asthma events in National Health and Nutrition Examination Survey subjects. Journal of Allergy and Clinical Immunology. 2013;132:821.