Table 1– Baseline patient characteristics
Non-purulentPurulentp-value
Subjects n3439
Age yrs71±9.671±9.70.87
Male32 (94)37 (95)0.68
Comorbidities3 (2–4)3(2–4)0.97
BMI0.29 (0.27–0.32)0.27 (0.24–0.30)0.63
Smokers34 (100)39 (100)0.98
Current smokers23 (68)22 (58)0.65
Pack-yrs60 (50–90)60 (40–80)0.57
Predicted FEV1 mL1216±4011280±3670.57
Predicted FEV1 %43.7±17.744.6±15.040.65
Predicted FVC mL2556±8912559±5570.84
FEV1/FVC %50.1±15.750.0±13.360.89
Severity of COPD#
GOLD stage
 II5 (16)9 (24)0.73
 III9 (29)10 (26)0.89
 IV17 (55)19 (50)0.80
Domiciliary oxygen10 (29)6 (15)0.15
MRC dyspnoea scale
 0–225 (74)31 (80)0.54
 ≥39 (27)8 (21)0.74
Acute exacerbations in the previous yr2.8±1.82.4±1.20.14
Inhaled corticosteroids33 (97)38 (97)0.46
  • Data are presented as mean±sd, n (%) or median (interquartile range), unless otherwise specified. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; COPD: chronic obstructive pulmonary disease; GOLD: Global Initiative for Chronic Obstructive Lung Disease; MRC: Medical Research Council. #: classification of severity of COPD based on lung function tests performed in stable phase.