Asthma affects individuals of every age group, gender, race, and socioeconomic status. Diagnosis is an important step in developing a personalized treatment approach that can benefit the patient. Fractional exhaled nitric oxide (FeNO) is an endogenous gaseous molecule that is expelled in human breath and can be measured to determine airway inflammation. It has been studied extensively over the years and is a common adjunctive tool in asthma diagnosis and management.

For a study published in the Journal of Asthma, Laura Chen, MD, and colleagues investigated whether FeNO testing can lead to a change in the diagnosis of asthma, focusing on an urban pediatric population. The team investigated the association of baseline and follow-up results with disease burden in minority children with persistent asthma

Minority Children Observed in Urban Asthma Center

The team created a retrospective chart review of 352 African American and Hispanic children who were observed at an urban asthma center in Bronx, NY. Children with low, intermediate, and high baseline FeNO levels were compared while applying demographics, clinical characteristics, and pulmonary function tests (PFT). Mixed-effects linear regression models were applied to 95 of these children with subsequent follow-up visits.

Baseline comorbidities that were considered included eczema, allergic rhinitis, reflux, gasping for air, snoring, and excessive daytime sleepiness. Baseline environmental exposures that were also considered included smokers in the home, humidifiers, rugs, curtains, mold, cockroaches, mice, rats, dogs, cats, and stuffed toys.

FeNO Levels Associated With Lower Airway Obstruction

Children with an intermediate (54%) FeNO level and children with a high (58%) FeNO level had lower airway obstruction compared to those who had low (33%) FeNO levels. Intermediate FeNO levels corresponded with more annual hospitalizations (2.8±6.2) compared with low and high FeNO levels (1.3±2.8 and 1.3±2.5). No differences in these comparative results were noted among varying ethnicities.

A multifactorial analysis linking multiple hospitalizations and lower airway obstruction with several covariates found that a change in FeNO coincided with two or more hospitalizations in the past 12 months with a relative risk reduction of 1.0 (CI 95%, 0.99-1.04). This analysis also found that a change in FeNO coincided with lower airways obstruction (FEV1/ FVC <80) with an OR of 1.0 (CI 95%, 0.98-1.01). An increase in FeNO over time was as sociated with higher BMI z-scores in the children (β=6.2; 95% CI, 1.0-11.4) (Table).

Lower Airway Obstruction Associated With Hospitalizations

The correlation between changes in asthma controller medications to changes in FeNO levels over time were also examined. Of 66 patients who had no change made to their asthma controller medication, 75.8% experienced no change or increase in FeNO, and 24.2% experienced a decrease in FeNO. Of the 13 patients who had a step up in their asthma controller medication, 69.2% had no change or increase in FeNO and 30.8% experienced a decrease in FeNO. Of the 16 patients who had a step down in their asthma controller medication, 75% had no change or increase in FeNO and 25% experienced a decrease in FeNO.

Dr. Chen and her team concluded that lower airway obstruction and hospitalizations are associated with the detection of intermediate and high FeNO levels. Thereby, initial and consistent FeNO measurements can be a helpful add-on tool in identifying asthma-related morbidity in urban African American and Hispanic children.