TABLE 1.
Demographics and clinical characteristics of the study population
| Non-asthma controls | Non-neutrophilic asthma | Neutrophilic asthma | p-value | |
| Subjects n | 8 | 36# | 9 | |
| Age years | 57 (34.5–65.5) | 58.5 (42–70) | 67 (56–72) | 0.329 |
| Sex female | 7 (87.5%) | 20 (55.6%) | 6 (66.7%) | 0.272 |
| BMI kg·m−2 | 24.6±3.7 | 31.0±6.0* | 29.0±6.2 | 0.020 |
| Ex-smoker | 1 (12.5%) | 5 (13.9%) | 0 (0%) | 0.667 |
| Smoking exposure pack-years | 4.4 (4.4–4.4) | 1 (0.45–1.45) | 0.380 | |
| Pre-bronchodilator FEV1 % pred | 99.7±20.9 | 81.8±19.0* | 72.5±17.1* | 0.009 |
| Pre-bronchodilator FVC % pred | 99.1±11.3 | 90.3±15.4 | 86.7±15.9 | 0.217 |
| 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 ICS | 0 (0%) | 32 (88.9%)* | 8 (88.9%)* | <0.001 |
| ICS dose BDP equivalent µg | 1000 (500–1600) | 1000 (500–2000) | 0.851 | |
| ACQ6 score | 1.17 (0.5–1.83) | 1.33 (1.0–2.17) | 0.509 | |
| Total sputum cell count ×106 cells·mL−1 | 8.33 (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−1 | 2.41 (0.42–6.08)¶ | 1.58 (0.70–3.14)¶ | 9.23 (3.77–13.4) | 0.001 |
| Sputum eosinophils ×106 cells·mL−1 | 0 (0–0.01) | 0.16 (0.03–0.29)* | 0.06 (0.03–0.17)* | 0.001 |
| Sputum macrophages ×106 cells·mL−1 | 3.79 (2.24–6.22) | 2.28 (1.48–3.10) | 1.83 (0.76–2.31) | 0.095 |
| Sputum lymphocytes ×106 cells·mL−1 | 0.21 (0.05–0.51) | 0.10 (0.04–0.19) | 0.03 (0.01–0.17) | 0.373 |
| Columnar epithelial cells ×106 cells·mL−1 | 0.03 (0.02–0.04) | 0.13 (0.02–0.30) | 0.10 (0.08–0.33) | 0.349 |
| Blood eosinophils ×109 cells·mL−1 | 0.10 (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.