Exhaled nitric oxide levels in asthma: Personal best versus reference values

Area of Science:

• Respiratory Medicine
• Clinical Chemistry
• Pulmonology

Background:

• Fraction of exhaled nitric oxide (FeNO) interpretation is complex due to multiple influencing factors.
• Clinically optimal FeNO levels for airways disease assessment remain undefined.

Purpose of the Study:

• To correlate FeNO levels with predicted values from Olin et al., Travers et al., and Dressel et al. equations.
• To compare FeNO levels after oral prednisone with those during optimized inhaled fluticasone treatment.

Main Methods:

• FeNO measurements were taken before and after a 14-day course of oral prednisone (30mg/d).
• FeNO data were compared with a prior study involving inhaled corticosteroid dose optimization based on FeNO or symptoms/lung function.

Main Results:

• FeNO levels post-prednisone (17.7 ppb) were significantly lower than during optimized fluticasone (20.2 ppb) or loss of asthma control (27.6 ppb).
• Post-prednisone FeNO levels closely matched Olin et al. predictions but were lower than Travers et al. and Dressel et al. predictions.
• Asthma control was achieved with inhaled corticosteroids despite FeNO levels exceeding predictions.

Conclusions:

• Oral steroid treatment provides a better reference for optimal FeNO levels, approximating Olin et al. predictions.
• Targeting FeNO solely on reference values is not clinically justified.
• Effective asthma control can be achieved with inhaled corticosteroids even when FeNO levels are higher than predicted values.