| Characteristics | 2 weeks | 4 weeks | p-value |
| Subjects n | 85 | 42 | |
| Age yrs | 20 (20–21) | 20 (20–21) | 0.863 |
| History of allergic disease | 8 (10) | 3 (10) | 1.000 |
| Time from initiation of smoking to presentation days# | 17 (14–28) | 16 (11–24) | 0.435 |
| Symptoms | |||
| Cough | 80 (94) | 40 (95) | 1.000 |
| Dyspnoea | 78 (92) | 41 (98) | 0.269 |
| Fever | 69 (81) | 41 (98) | 0.011 |
| Chill | 46 (54) | 26 (62) | 0.405 |
| Headache | 28 (33) | 11 (26) | 0.438 |
| Myalgia | 27 (32) | 3 (7) | 0.002 |
| Chest pain | 13 (15) | 5 (12) | 0.606 |
| Inspiratory crackle on chest auscultation | 53 (62) | 35 (83) | 0.016 |
| Laboratory findings | |||
| Leukocytosis >10000 cells·μL−1 | 59 (69) | 33 (79) | 0.277 |
| Peripheral eosinophilia >500 cells·μL−1 | 32 (38) | 8 (19) | 0.034 |
| C-reactive protein mg·dL−1 | 12.1 (5.9–31.4) | 35.6 (16.3–38.4) | <0.001 |
| Pa,O2/FI,O2 ratio | 298.7 (262.9–344.8) | 239.1 (219.3–268.8) | <0.001 |
| Eosinophils on BAL % | 40 (35–53) | 40 (31–50) | 0.078 |
| Lymphocytes on BAL % | 19 (12–26) | 23 (12–30) | 0.747 |
| Neutrophil on BAL % | 5 (2–10) | 6 (4–17) | 0.004 |
Data are presented as median (interquartile range) or n (%), unless otherwise stated. Pa,O2: arterial oxygen tension: FI,O2: inspiratory oxygen fraction; BAL: bronchoalveolar lavage. #: data were available in 131 (97%) patients who were current smokers.