TABLE 1

Demographics and clinical characteristics of the study population

Non-asthma controlsNon-neutrophilic asthmaNeutrophilic asthmap-value
Subjects n836#9
Age years57 (34.5–65.5)58.5 (42–70)67 (56–72)0.329
Sex female7 (87.5%)20 (55.6%)6 (66.7%)0.272
BMI kg·m−224.6±3.731.0±6.0*29.0±6.20.020
Ex-smoker1 (12.5%)5 (13.9%)0 (0%)0.667
Smoking exposure pack-years4.4 (4.4–4.4)1 (0.45–1.45)0.380
Pre-bronchodilator FEV1 % pred99.7±20.981.8±19.0*72.5±17.1*0.009
Pre-bronchodilator FVC % pred99.1±11.390.3±15.486.7±15.90.217
Pre-bronchodilator FEV1/FVC %81.0 (73.9–83.3)71.1 (63.3–79.3)*71.1 (54.4–76.0)*0.012
Taking ICS0 (0%)32 (88.9%)*8 (88.9%)*<0.001
ICS dose BDP equivalent µg1000 (500–1600)1000 (500–2000)0.851
ACQ6 score1.17 (0.5–1.83)1.33 (1.0–2.17)0.509
Total sputum cell count ×106 cells·mL−18.33 (4.32–9.68)5.22 (3.29–7.11)11.25 (5.13–16.83)0.028
Sputum neutrophils %32 (9.0–52.75)36.5 (20.25–50.63)73.5 (68.0–82.0)<0.001
Sputum eosinophils %0 (0–0.13)2.25 (0.75–7.88)*1.0 (0.4–1.5)<0.001
Sputum macrophages %48.75 (41.38–87.63)49.25 (38.0–62.13)16.25 (13.75–26.0)<0.001
Sputum lymphocytes %3.25 (1.5–4.38)2.13 (1.25–3.13)0.75 (2.0–2.25)0.121
Columnar epithelial cells %0.25 (0.25–0.75)2.63 (0.38–6.88)1.8 (0.5–8.25)0.239
Sputum neutrophils ×106 cells·mL−12.41 (0.42–6.08)1.58 (0.70–3.14)9.23 (3.77–13.4)0.001
Sputum eosinophils ×106 cells·mL−10 (0–0.01)0.16 (0.03–0.29)*0.06 (0.03–0.17)*0.001
Sputum macrophages ×106 cells·mL−13.79 (2.24–6.22)2.28 (1.48–3.10)1.83 (0.76–2.31)0.095
Sputum lymphocytes ×106 cells·mL−10.21 (0.05–0.51)0.10 (0.04–0.19)0.03 (0.01–0.17)0.373
Columnar epithelial cells ×106 cells·mL−10.03 (0.02–0.04)0.13 (0.02–0.30)0.10 (0.08–0.33)0.349
Blood eosinophils ×109 cells·mL−10.10 (0.09–0.16)0.24 (0.17–0.31)*0.19 (0.15–0.24)0.026

Data are presented as median (interquartile range) or mean±sd, unless otherwise stated. The Kruskal–Wallis test was used for non-parametric data, Fisher's exact test for proportions and one-way ANOVA for normally distributed data with Bonferroni corrections. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; ICS: inhaled corticosteroids; BDP: beclomethasone dipropionate; ACQ6: six-item Asthma Control Questionnaire. #: 14 (39%) eosinophilic asthma and 22 (61%) paucigranulocytic asthma. *: p<0.05 versus non-asthma controls; : p<0.05 versus neutrophilic asthma. Statistically significant results are highlighted in bold.