Comparison of participants with neutrophilic and non-neutrophilic sputum samples
| Neutrophilic inflammation | No neutrophilic inflammation | p Value | |
| Number of subjects | 67 | 204 | |
| Age (years), mean (range) | 59.9 (32.5–78.9) | 55.0 (18.9–85.9) | 0.063 |
| Sex, man, n (%) | 34 (50.7) | 83 (40.7) | 0.158 |
| Atopic, n (%) | 43 (66.1), n=65 | 149 (75.6), n=197 | 0.147 |
| Ex-smoker, n (%) | 27 (40.3) | 73 (35.8) | 0.560 |
| Pack years, median (q1,q3) | 7.5 (1.5, 25.0) n=27 | 7.7 (0.7, 26.0), n=70 | 0.871 |
| FEV1 % predicted, mean (SD) | 72.6 (17.5) | 81.1 (19.0) | 0.001 |
| FEV1/FVC (%), mean (SD) | 68.1 (10.6) | 70.9 (10.5) | 0.075 |
| ICS dose* (µg/day), median (q1,q3) | 1000 (800, 2000), n=53 | 1000 (570, 2000), n=156 | 0.639 |
| Sputum cell counts, median (q1,q3) | |||
| Total cell number (×101 cells/mL) | 8.6 (3.6, 13.5), n=66 | 3.1 (1.9, 4.9), n=202 | <0.001 |
| Viability (%) | 90.2 (83.5, 95.8) | 77.1 (63.8, 86.4) | <0.001 |
| Neutrophils (%) | 76.0 (70.2, 83.2) | 34.9 (21.2, 47.0) | <0.001 |
| Neutrophil† (×101/mL) | 623.5 (286.2, 1186.4) | 95.0 (42.6, 182.7) | <0.001 |
| Eosinophils (%) | 1.2 (0.5, 2.5) | 1.5 (0.5, 7.9) | 0.069 |
| Eosinophil† (×102/mL) | 6.7 (3.6, 20.9) | 4.5 (0.9, 28.2) | 0.137 |
| Macrophages (%) | 17.7 (13.2, 23.0) | 55.7 (41.0, 66.9) | <0.001 |
| Macrophage† (×104/mL) | 124.5 (59.3, 241.6) | 162.6 (96.0, 268.5) | 0.057 |
| Lymphocytes (%) | 0.5 (0.0, 1.2) | 0.7 (0.2, 1.5) | 0.178 |
| Lymphocyte† (×104/mL) | 3.4 (0.0, 9.2) | 1.9 (0.2, 4.9) | 0.039 |
| Columnar epithelial cells (%) | 0.7 (0.2, 1.7) | 1.7 (0.5, 5.2) | <0.001 |
| Columnar epithelial cells† (×104/mL) | 4.4 (0.8, 8.5) | 4.4 (1.0, 12.1) | 0.576 |
| CXCL-8 (ng/mL), median (q1, q3) | 17.9 (6.3, 70.0), n=28 | 6.1 (2.2, 11.9), n=75 | <0.001 |
| Sputum culture performed, n (%) | 36 (53.7) | 103 (50.5) | 0.674 |
| Positive culture, n (%) | 13 (36.1) | 8 (7.8) | <0.001 |
| Purulent sputum, n (%) | 33 (49.2) | 44 (21.6) | <0.001 |
| Sputum colour, n (%) | |||
| 1 | 11 (16.4) | 47 (23.0) | 0.304 |
| 2 | 23 (34.3) | 113 (55.4) | 0.003 |
| 3 | 27 (40.3) | 41 (20.1) | 0.002 |
| 4 | 5 (7.5) | 3 (1.5) | 0.024 |
| 5 | 1 (1.5) | 0 (0.0) | 0.247 |
*ICS dose is calculated as beclomethasone equivalent dose, where 1 µg of beclomethasone=1 µg budesonide=0.5 µg fluticasone.
†Cell numbers represent data from 66 and 202 patients with neutrophilic and no neutrophilic inflammation subgroups, respectively.
FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; ICS, inhaled corticosteroids; n, number of participants; q, quartile.