The following is a summary of the “Sex differences of small airway function and fractional exhaled nitric oxide in patients with mild asthma,” published in the February 2023 issue of Allergy and Clinical Immunology by Zhang, et al.

For a study, researchers aimed to compare the sex ratios of SAF and FeNO in patients with positive methacholine challenge test (MCT) results for moderate asthma. The 1,609 adults who participated in this cross-sectional, double-centered observational study had a forced expiratory volume in 1 second greater than or equal to 80% and displayed symptoms consistent with asthma. In addition, male and female spirometry data, FeNO and impulse oscillometry readings, and peripheral blood test results were compared. 

SAF parameters and FeNO’s receiver-operating characteristic curves for predicting a successful MCT outcome were also determined. Among age-matched patients with mild asthma, males had superior SAF but higher FeNO levels (60 [29.27%] vs. 187 [46.75%] for small airway dysfunction; 78.6% vs. 72.0% for forced expiratory flow [FEF]_50%; 67.5% vs. 60.1% for FEF_75%.; 73.7% vs. 67.4% for FEF_25%-75%; and 42.0 ppb vs. 29 ppb for FeNO, respectively, all P ≤ .001). Comparing male smokers to nonsmokers, current smokers had significantly lower FeNO levels. 

Age was a more significant factor in reducing SAF and FeNO values in female asthma patients than in male patients. Males with FEF_25%-75%, FEF_50%., and FeNO of 41.0 ppb had a higher likelihood of a positive MCT result than females with FEF_25%-75%, FEF_50%., and FeNO of 35.0 ppb. Female individuals fare worse when comparing SAF and FeNO levels across male and female patients with moderate asthma. When determining if SAF characteristics (FEF_25%-75%, FEF_50%), alone or in combination with FeNO, can reliably predict a positive MCT result in asthma diagnosis, it is important to take sex into account when determining appropriate cutoff values.

Source: sciencedirect.com/science/article/abs/pii/S1081120622019160