| Normal(n = 11) | COPD ex-smokers(n = 5) | COPD smokers(n = 10) | Asthma(n = 11) | |
| Male/female | 5/6 | 5/0 | 10/0 | 9/2 |
| Age (years) | 37 (21–42) | 69 (61–73) | 63 (53–71) | 27 (18–41) |
| Atopy | – | – | – | + |
| PC20 (FEV1) (mg/ml) | >16 | N/A | N/A | 2.72 (0.52–6.96) |
| FEV1 (% predicted) | 110 (92–135) | 30 (21–52) | 46 (23–68) | 102 (89–116) |
| FEV1/FVC (%) | 86 (72–92) | 41 (24–46) | 56 (31–63) | 82 (71–100) |
| Smoking history (pack years) | Non-smokers | 98 (45–129) | 43 (24–102) | Non-smokers |
| Stop years (years) | N/A | 3 (1–12) | 0 | N/A |
FEV1 forced expiratory volume in 1 s; FVC, forced vital capacity; PC20, concentration of histamine that causes a 20% fall in FEV1; N/A, not applicable.
Data presented as median (range) or absolute values where appropriate.