Comparing spirometry, impulse oscillometry with computed tomography for assessing small airway dysfunction in subjects with and without chronic obstructive pulmonary disease

Table 3 Characteristics of 1862 subjects stratified by small airway dysfunction status based on impulse oscillometry and computed tomography diagnosis

Variable	No SAD with IOS and CT^§ (n = 1010)	Combined IOS and CT-defined SAD^¶ (n = 274)	Only IOS-defined SAD^# (n = 330)	Only CT-defined SAD^** (n = 248)	P value
Age, year	58.7 ± 7.6	66.6 ± 6.5^*	61.1 ± 8.3^*†	65.9 ± 6.7^*‡	< 0.001
Male, n (%)	705 (69.8)	252 (92.0)^*	187 (56.7)^*†	232 (93.5)^*‡	< 0.001
BMI, kg/m²	23.1 ± 3.0	21.1 ± 3.2^*	24.6 ± 3.1^*†	20.7 ± 2.7^*‡	< 0.001
Smoking status, n (%)					< 0.001
Never smoked	424 (42.0)	28 (10.2)^*	164 (49.7)^†	34 (13.7)^*‡
Former smoked	154 (15.2)	110 (40.1)^*	53 (16.1)^†	69 (27.8)^*†‡
Current smoked	432 (42.8)	136 (49.6)	113 (34.2)^*†	145 (58.5)^*‡
Smoking index, pack-years	24.6 ± 31.5	40.1 ± 33.4^*	22.1 ± 31.3^†	31.8 ± 26.5^*†‡	< 0.001
Biomass exposure, n (%)	343 (34.0)	116 (42.3)	119 (36.1)	87 (35.1)	0.084
Occupational history of dusts/gases/fumes, n (%)	187 (18.5)	75 (27.4)^*	57 (17.3)^†	62 (25.0)	0.001
Family history of respiratory diseases, n (%)	111 (11.0)	56 (20.4)^*	40 (12.1)^†	38 (15.3)	< 0.001
Clinical symptoms, n (%)
Wheeze	61 (6.0)	78 (28.5)^*	47 (14.2)^*†	23 (9.3)^†	< 0.001
Cough	200 (19.8)	147 (53.6)^*	82 (24.8)^†	90 (36.3)^*†‡	< 0.001
Sputum	263 (26.0)	173 (63.1)^*	115 (34.8)^*†	106 (42.7)^*†	< 0.001
Dyspnea	206 (20.4)	174 (63.5)^*	93 (28.2)^*†	88 (35.5)^*†	< 0.001
Acute respiratory events in the prior year, n (%)	62 (6.1)	57 (20.8)^*	35 (10.6)^*†	31 (12.5)^*	< 0.001

Data are shown as mean ± standard deviation or n (%). ^* Significantly different from No SAD with IOS and CT (P < 0.05). ^† Significantly different from Combined IOS and CT-defined SAD (P < 0.05). ^‡ Significantly different from Only IOS-defined SAD (P < 0.05). ^§ No SAD diagnosed by both IOS and CT. ^¶ SAD diagnosed by both IOS and CT. ^# SAD diagnosed by only IOS but not CT. ^**SAD diagnosed by only CT but not IOS. Abbreviations: IOS, impulse oscillometry; CT, computed tomography; SAD, small airway dysfunction; BMI, body mass index

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