While fractional exhaled nitric oxide (FeNO) has been shown to have potential as a prognostic biomarker in asthma, a recent study attempted to provide more concrete proof of the benefits of its potential use.
In an article published in The Lancet Respiratory Medicine, the authors noted that FeNO "is becoming an accepted as a biomarker that can be used to assess the extent of underlying type 2 airway inflammation in asthma, and one that can potentially inform the management of patients with moderate-to-severe asthma." The authors added that its use is limited, in part because of a "lack of prognostic data that can guide clinicians" on how to use it.
Researchers conducted a post-hoc analysis of the 52-week phase 3 LIBERTY ASTHMA QUEST study, identifying more than 600 moderate-to-severe asthma patients in the trial's placebo arm. The patients evaluated all met other criteria, including having uncontrolled asthma with inhaled glucocorticoids and up to two controllers, and had one or more exacerbations in the previous year. The annualized severe exacerbation rate was assessed by baseline FeNO (<25 ppb, ≥25 to <50 ppb, ≥50 ppb; negative binomial model) and cross-classified by baseline blood eosinophils (<150 cells per μL, ≥150 to <300 cells per μL, ≥300 cells per μL), and prior exacerbations, all of which had been adjusted for various clinical characteristics.
In their findings, the authors noted that patients with a baseline FeNO of 50 ppb or higher had a 1.54 times higher exacerbation rate than those with FeNO of less than 25 ppb (relative risk 1.54 [95% CI, 1.11-2.14]; P=0.0097). Patients with a baseline FeNO of 25 to <50ppb had a 1.33 times higher exacerbation rate than those with a FeNO of less than 25 ppb (1.33[0.99-1.78]; P=0.0572). The researchers also noted that patients with baseline FeNO of 25 ppb or higher, a blood eosinophil count of 150 cells per μL or higher, and two or more prior exacerbations, had an exacerbation rate 3.62 times higher than those with FeNO of less than 25 ppb, blood eosinophil counts under 15 cells per μL, and one prior exacerbation (3.62[1.67-7.81]; P=0.0011).
"Our finding of the additive prognostic value of FeNO is in keeping with previous studies in a community population, and two more limited analyses of severe asthma. Similarly, a study of severe asthma patients showed that FeNO was a risk factor for chronic corticosteroid use when analyzed independently from type 2 biomarkers such as eosinophil count," the authors said in the article. "This additional prognostic effect is predictable, as the two biomarkers are distinct and reflect largely different, albeit partially overlapping, cytokine pathways involved in type 2 airway inflammation."
While the authors said their research included several statistical comparisons, they suggested more analysis was needed to confirm their findings.
