Patients with severe asthma who had high levels of fractional exhaled nitric oxide (FeNO) were more likely to have asthma exacerbations than those with low levels, according to findings presented at the 2021 American Thoracic Society (ATS) International Conference, held virtually from May 14 to 19, 2021. Using data from a 3-year prospective observational cohort study, researchers sought to examine the association between long-term changes in FeNO and the development of severe asthma exacerbations.

Of the participants in the Hokkaido Severe Asthma Cohort Study who had annual monitoring of FeNO at baseline, 100 patients with severe asthma completed a 3-year follow-up in which FeNO was measured annually. Participants were classified into 3 groups according to FeNO levels at baseline, 1 year, and 2 years.  The sustained high group had FeNO above 50 ppb for all 3 visits, the sustained low group had levels below 25 ppb for all 3 visits, and the intermediate group did not fit into the other 2 categories. Participants in the intermediate group were further categorized based on the median value of the coefficient of variation (CV) of FeNO during the 3 years.

Patients in the sustained high group had shorter exacerbation-free survival and more frequent exacerbations than those in the sustained low group (median number of exacerbation events, 3 vs 0; P =.01). Patients within the intermediate category who were considered part of the high CV group experienced shorter exacerbation-free survival vs the low CV group. The CV of FeNO was an independent contributing factor for the early onset of the first exacerbation event and frequency of exacerbations in multivariate analysis.

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“Persistence of FeNO above 50 ppb over the years as well as the presence of large variations in FeNO levels were associated with the development of exacerbations in patients with severe asthma,” the study authors wrote.


Abe Y, Suzuki M, Kimura H, et al. Annual fractional exhaled nitric oxide measurements and exacerbations in severe asthma. Presented at: the American Thoracic Society (ATS) International Conference 2021; May 14-19, 2021. Abstract A1432.

This article originally appeared on Pulmonology Advisor