Can Baseline FeNO Levels Predict Severe Asthma Exacerbations?

A nice Young woman using asthma inhaler at home

Fraction exhaled nitric oxide (FeNO) serves as a biomarker for type 2 inflammation. A study published as part of the AAAAI Annual Meeting measured the value of baseline FeNO levels for subsequent severe asthma exacerbations in patients with uncontrolled, moderate-to-severe disease who were receiving placebo in the dupilumab phase III QUEST study.

To be eligible for inclusion, patients had to have moderate-to-severe asthma uncontrolled with inhaled glucocorticoids plus ≤2 controllers, history of ≥1 exacerbation in prior year, forced expiratory volume percent predicted ≤80%, and Asthma Control Questionnaire score ≥1.5. There was no requirement for baseline type 2 biomarkers. Over the 52-week treatment period, annualized severe asthma exacerbation rate was evaluated per baseline FeNO levels (<25, 25-49, ≥50 ppb) in 620 patients assigned to placebo, and further stratified by baseline blood eosinophils (<150, 150-299, ≥300 cells/μL).

Patients with baseline FeNO ≥50 ppb, compared with those with baseline FeNO <2 5ppb, were 1.54 times as likely to have exacerbations when adjusting for baseline eosinophils and other clinical characteristics (95% confidence interval [CI], 1.11-2.14). Patients with baseline FeNO ≥50 ppb and eosinophils ≥300 cells/μL were 3.19 times as likely to have exacerbations compared with patients with baseline FeNO <25 ppb and eosinophils <150 cells/μL when controlling for possible differences in other clinical characteristics (95% CI, 1.62-6.28).

“In [patients with] uncontrolled, moderate-to-severe asthma, higher baseline FeNO levels were associated with higher severe asthma exacerbation rates over the subsequent 52 weeks, independent of standard clinical characteristics; risk was particularly high in patients also having blood eosinophils ≥300 cells/μL. These results suggest that FeNO, independently and in combination with blood eosinophils, identifies patients at increased risk of subsequent exacerbations,” the researchers concluded.

https://www.jacionline.org/article/S0091-6749(19)32494-7/fulltext