FeNO (Fractional exhaled Nitric Oxide) is a non-invasive biomarker used to measure the level of nitric oxide in the breath, which is an indicator of airway inflammation, particularly in the context of asthma.
- Measurement Process:
- FeNO is measured using a specialized device that requires the patient to exhale steadily into a mouthpiece.
- The device then analyzes the concentration of nitric oxide in the exhaled air, usually expressed in parts per billion (ppb).
- Clinical Use:
- Asthma Diagnosis and Management: FeNO levels can help in diagnosing asthma and determining the degree of eosinophilic inflammation in the airways. High FeNO levels typically indicate the presence of airway inflammation, which is often associated with allergic or eosinophilic asthma.
- Monitoring Response to Treatment: FeNO can be used to monitor the effectiveness of inhaled corticosteroids, which are commonly prescribed to reduce airway inflammation in asthma patients. A decrease in FeNO levels following treatment suggests a positive response.
- Predicting Exacerbations: Elevated FeNO levels may indicate an increased risk of asthma exacerbations, making it a useful tool for predicting and preventing flare-ups.
- Interpretation of Results:
- Low FeNO (<25 ppb in adults, <20 ppb in children): Suggests a low likelihood of eosinophilic airway inflammation and asthma.
- Intermediate FeNO (25-50 ppb in adults, 20-35 ppb in children): May indicate mild eosinophilic inflammation, and results should be interpreted in the context of other clinical findings.
- High FeNO (>50 ppb in adults, >35 ppb in children): Typically indicates significant eosinophilic airway inflammation, often associated with poorly controlled asthma or a need for an increase in anti-inflammatory treatment.
- Advantages of FeNO Testing:
- Non-invasive and Painless: The test is simple and does not require blood samples or invasive procedures.
- Quick and Convenient: Results are available almost immediately, making it a practical tool in clinical settings.
- Guides Tailored Treatment: FeNO can help in tailoring asthma treatment by identifying patients who are more likely to benefit from inhaled corticosteroids.
- Limitations:
- Not Specific to Asthma: While FeNO is useful for detecting eosinophilic inflammation, it is not specific to asthma and can be elevated in other conditions like allergic rhinitis or eosinophilic bronchitis.
- Affected by External Factors: FeNO levels can be influenced by factors such as smoking, respiratory infections, and atopy, which may affect the interpretation of results.