Converting F_ENO by different flows to standard flow F_ENO.

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Clinical Diagnostics

Background:

• Fractional exhaled nitric oxide (F_ENO) is a biomarker for eosinophilic airway inflammation.
• Current F_ENO measurement is standardized to an expiratory flow rate of 50 mL/s.
• Variations in expiratory flow rate affect F_ENO results, hindering data comparison.

Purpose of the Study:

• To develop and validate a conversion model for F_ENO measurements across different expiratory flow rates.
• To enable standardized comparison of F_ENO data in clinical and research settings.

Main Methods:

• A conversion model was developed using F_ENO data from 30 volunteers measured at 50, 30, 100, and 300 mL/s.
• The model was validated in five external populations: healthy adults, healthy children, and patients with COPD, asthma, and alveolitis.

Main Results:

• The conversion model showed low deviation in healthy adults (-0.44 ppb) and children (0.27 ppb) when converting from 100 mL/s to 50 mL/s.
• Deviations in patients with COPD (-1.16 ppb), asthma (-1.68 ppb), and alveolitis (1.47 ppb) were also assessed.
• The model is suitable for large epidemiological data but not for individual patient-level conversion.

Conclusions:

• A validated model exists to convert F_ENO measurements from various expiratory flow rates to the standard 50 mL/s.
• This model facilitates the comparison of F_ENO data in diverse populations, including those with obstructive lung diseases.
• The conversion is applicable for epidemiological studies but not recommended for individual clinical decisions.