Table 1– Baseline differences between the initial cohort and the study population, and the Pseudomonas aeruginosa culture-positive and culture-negative groups.

	Initial cohort	Study population	p-value^#	P. aeruginosa culture-positive group	P.aeruginosa culture-negative group	p-value^¶
Subjects n	380	132		66	66
Age years	65.4±10.9	68±8.8	0.011	68±8.8	68.3±9	0.969
Sex %
Male				51.1	51.1	0.999
Female				47.4	47.4
BMI m·kg⁻²	24.7±5.2	24±6.3	0.257	23.6±5.8	24.4±6.8	0.497
FEV₁ % predicted	38.6±20.1 (9–81.1)	33.6±14.7 (12.6–72.4)	0.008	33.4±14.5 (12.6–72.4)	33.8±14.9 (12.9–71)	0.882
FEV₁/FVC %	40.6±21.2 (13–69.8)	36.1±16.8 (13.5–69.8)	0.029	35±12.1 (14.1–69.8)	37.2±20.7 (13.5–69.5)	0.456
D_LCO % predicted	43.7±18.1	40.8±17.4	0.157	41.5±18.2	40.1±16.7	0.663
K_CO % predicted	54.8±21.6	54±22.1	0.747	55.5±21.8	52.5±22.4	0.448
TLC % predicted	123.7±19.6	122.7±17	0.662	121.1±18.1	124.5±15.6	0.286
RV % predicted	205.1±61.9	203.3±53	0.780	206±52.8	200.5±53.6	0.569
RV/TLC	155.2±32.7	157±32.1	0.639	60.3±9.8	59.4±11.6	0.647
P_aO₂ kPa	9.5±1.4	9.0±1.5	0.014	9.1±1.4	8.9±1.8	0.440
P_aCO₂ kPa	5.3±0.8	5.5±1.1	0.116	5.3±0.9	5.8±1.4	0.018
Exacerbations per year	1.9±0.7	2.1±0.7	0.086	2.3±0.7	1.9±0.7	0.008

Data are presented as mean±sd or mean±sd (range), unless otherwise stated. Bold signifies statistical significance. BMI: body mass index; FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; D_LCO: diffusing capacity of the lung for carbon monoxide; K_CO: transfer coefficient of the lung for carbon monoxide; TLC: total lung capacity; RV: residual volume; P_aO₂: arterial oxygen tension; P_aCO₂: arterial carbon dioxide tension. ^#: level of significance for comparison between the initial cohort and the study population; ^¶: level of significance for comparison between the P. aeruginosa culture-positive and culture-negative groups.