Abstract Blood eosinophils and FeNO are asthma biomarkers that predict response to Type-2 biologic therapies. Studies suggest that combining biomarkers of two different compartments, one blood and one airway, leads to greater prognostic value, but the reasons for this effect are poorly understood(Meulmeester,2025;Castro,2015). We hypothesized that adult and pediatric patients with elevations in both blood eosinophils and FeNO would have more severe and poorly controlled asthma, more airway inflammation and distinct inflammatory profiles by RNA sequencing. Methods Adult(18yo) and pediatric(16yo) patients enrolled in the Severe Asthma Research Program(SARP,2012-2015) were categorized by their baseline blood eosinophil counts(±300/uL) and FeNO( ± 25ppb) into 4 categorial groups: Hi-Eos/Hi-FeNO, Hi-Eos/Lo-FeNO, Lo-Eos/Hi-FeNO and Lo-Eos/Lo-FeNO. The ability of the biomarker groups to predict exacerbations at one- and two-years post-enrollment was analyzed using regression models in the adult and pediatric cohorts. Sputum bulk RNA sequencing data (performed at National Jewish/Seibold; Fahy, 2025) were assessed for differential gene expression between biomarker groups (log2fold-change threshold 0.5, false-discovery-rate 0.1). Pathway enrichment analysis was performed with g:Profiler and prior knowledge. Results 522 adult and 168 pediatric asthma patients were included. There were few demographic differences in the 4 groups, although Hi-Eos/Hi-FeNO adults had lower BMI despite similar corticosteroid use compared to the other groups. Hi-Eos/Hi-FeNO adult patients had 2.26 and 2.03-times the 1- and 2-year exacerbation rates compared to the Lo-Eos/Lo-FeNO patients, with trends to lower FEV1% predicted and Asthma Control Test scores. In pediatric patients, biomarker groups did not predict asthma control, including exacerbations. Hi-Eos/Hi-FeNO adult patients had higher sputum eosinophils. Differential gene expression analysis (sputum) from subsets (43% to 54%) of the 4 groups identified upregulation of 816 and downregulation of 50 genes comparing the Hi-Eos/Hi-FeNO to Lo-Eos/Lo-FeNO groups. Not surprisingly, upregulated genes included those related to mast cells, type 2 inflammation and eosinophils. Pathway analysis showed unexpected enrichment in exogenous and endogenous lipid antigen binding molecular function pathways. Enriched biologic process pathways included those related to type 2 immunity, lysozyme localization, and cilia-related epithelial processes, despite epithelial cells being only 6% of sputum cell types. Conclusions Adult asthma patients with elevations in both blood eosinophils and FeNO had lower lung function, a two-fold higher exacerbation risk, increased eosinophilic airway inflammation and a unique sputum gene expression profile. Utilization of two easily available biomarkers can help identify high risk adult, but not pediatric, asthma patients. Sputum transcriptomics novelly identified enhanced lipid antigen presentation pathways, exploration of which could expand disease understanding. This abstract is funded by: U10 HL109172; U10 HL109168; U10 HL109152; U10 HL109257;U10 HL109146; U10 HL109250;U10 HL109164; U10 HL109086
Lisius et al. (Fri,) studied this question.