Breath volatile organic compounds and inflammatory markers in adult asthma patients: negative results from the ALLIANCE cohort

a) Patient demographics according to asthma phenotypes. Data are presented as median (interquartile range). Statistics: Kruskal–Wallis ANOVA. ICS: inhaled corticosteroids; OCS: oral corticosteroids; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; RV: residual volume; TLC: total lung capacity; sRtot: specific total airway resistance; R5Hz: resistance at 5 Hz; FDRabs: frequency dependence of resistance (resistance at 5 Hz minus resistance at 20 Hz). ^#: omalizumab or mepolizumab; ^¶: missing values. b) Gas chromatography/mass spectrometry chromatogram of one representative patient with inserts and arrows indicating the retention time (RT) for propanol-1, hexane, 2-hexanone and nonanal [3]. The black line indicates the total ion content (TIC), the insert coloured plots show specific masses of the respective volatile organic compounds (VOCs). c–e) Correlation between VOCs and sputum neutrophils (%). All patients and subgroup correlations not significant (unadjusted p-value >0.05). f) Correlation between hexane and sputum eosinophils (%). All patients and subgroup correlations not significant (unadjusted p-value >0.05), except for smokers (r=−0.45, unadjusted p-value 0.02, adjusted p-value 0.48). Selection of VOCs based on published data [3]. As shown in (b), 2-hexanone was not detectable in our samples. g) Histograms of unadjusted p-values for the correlation between all detected VOCs and sputum neutrophils and eosinophils (%), exhaled nitric oxide fraction (F_ENO) and blood eosinophils (%). a.u.: arbitrary units.