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

Table 1 Characteristics of 2052 subjects stratified by small airway dysfunction status based on spirometry and computed tomography diagnosis

Variable	No SAD with spirometry and CT^§ (n = 348)	Combined spirometry and CT-defined SAD^¶ (n = 562)	Only spirometry-defined SAD^# (n = 1118)	Only CT-defined SAD^** (n = 24)	P value
Age, year	56.0 ± 7.4	66.4 ± 6.6^*	60.3 ± 7.7^*†	64.8 ± 6.9^*‡	< 0.001
Male, n (%)	207 (59.5)	516 (91.8)^*	755 (67.5)^*†	18 (75.0)^†	< 0.001
BMI, kg/m²	23.9 ± 3.0	21.0 ± 3.0^*	23.4 ± 3.2^†	21.1 ± 2.0^*‡	< 0.001
Smoking status, n (%)					< 0.001
Never smoked	201 (57.8)	67 (11.9)^*	460 (41.1)^*†	12 (50.0)^†
Former smoked	44 (12.6)	198 (35.2)^*	179 (16.0)^†	3 (12.5)
Current smoked	103 (29.6)	297 (52.8)^*	479 (42.8)^*†	9 (37.5)
Smoking index, pack-years	17.5 ± 29.5	37.0 ± 31.2^*	25.3 ± 31.4^*†	16.7 ± 21.7^†	< 0.001
Biomass exposure, n (%)	114 (32.8)	218 (38.8)	391 (35.0)	9 (37.5)	0.268
Occupational history of dusts/gases/fumes, n (%)	48 (13.8)	142 (25.3)^*	217 (19.4)^†	2 (8.3)	< 0.001
Family history of respiratory diseases, n (%)	28 (8.0)	102 (18.1)^*	139 (12.4)^†	0 (0.0)	< 0.001
Clinical symptoms, n (%)
Wheeze	15 (4.3)	126 (22.4)^*	102 (9.1)^*†	0 (0.0)	< 0.001
Cough	61 (17.5)	258 (45.9)^*	249 (22.3)^†	1 (4.2)^†	< 0.001
Sputum	97 (27.9)	301 (53.6)^*	327 (29.2)^†	7 (29.2)	< 0.001
Dyspnea	58 (16.7)	290 (51.6)^*	277 (24.8)^*†	4 (16.7)^†	< 0.001
Acute respiratory events in the prior year, n (%)	13 (3.7)	101 (18.0)^*	96 (8.6)^*†	2 (8.3)	< 0.001

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

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