The normal range of FENO levels are:
| Adults |
5-25 ppb |
| Children (under 12 years old) |
5-20 ppb |
If a patient with normal FENO levels presents with asthma-like symptoms, other causes should be considered, e.g.: [Taylor 2006]
• Neutrophilic asthma
• Anxiety/hyperventilation
• Vocal cord dysfunction
• Gastroesophageal reflux
• Rhinosinusitis
• Cardiac disease
If the patient is a child, the following differential diagnoses should also be considered: [Taylor 2006]
• Wheezy bronchitis
• ENT disorders
• Immunodeficiencies
Read more on how FENO values were determined.