Quantitative computed tomography measurements of emphysema for diagnosing asthma-chronic obstructive pulmonary disease overlap syndrome

Figures & data

Table 1 Characteristics of participants

Characteristics	Controls (n=128)	Asthma (n=151)	COPD (n=125)	P-value
Age, years	59.8±8.5	58.2±9.4***	65.8±9.3*,#	<0.001a
Sex, female/male	49/79	81/70	32/93	<0.001b
BMI, kg/m^2	24.3±3.3	25.5±3.9**	22.6±4.5*,#	<0.001a
Smoking, pack-years	0	12.1±21.8*	34.5±26.6*,#	<0.001a
Current/former/never smoker	0/0/128	28/23/100	57/49/19	<0.001b
Acute exacerbations	NA	1.1±0.8	1.2±0.9	0.436c
Postbronchodilator
FEV1 % predicted	100.9±13.2	65.1±22.5*	44.3±18.6*,#	<0.001a
FVC% predicted	103.4±13.9	88.5±18.1*	73.6±17.5*,#	<0.001a
VC% predicted	103.9±13.2	88.9±17.1*	76.0±16.2*,#	<0.001a
FEV1/FVC%	81.3±5.2	60.5±13.9*	48.1±12.2*,#	<0.001a
Response to β2-agonist
ΔFEV1, L	NA	0.305±0.033	0.143±0.009	<0.001c
% change in FEV1 %	NA	22.4±16.4	15.2±12.8	<0.001c

Notes: Data are presented as mean ± SD.

* P<0.01,

** P<0.05,

*** P>0.05 versus controls;

# P<0.01 versus asthma patients.

a Analysis of Kruskal–Wallis test.

b Analysis of chi-square test.

c Analysis of Mann–Whitney U test.

Abbreviations: BMI, body mass index; ΔFEV₁, increases in forced expiratory volume in 1 second; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity;NA, not applicable; SD, standard deviation; VC, vital capacity.

Table 2 Emphysema measurements of asthma, COPD, and control participants

	Controls (n=128)	Asthma (n=151)	COPD (n=125)	P-value
%LAA-950, %	2.79±2.37	6.19±6.79*	15.84±11.90*,#	<0.001a
%LAA-910, %	21.07±20.06	26.20±18.78**	40.97±17.75*,#	<0.001a
LP10A, HU	−914.7±23.0	−924.1±32.0*	−954.3±25.9*,#	<0.001a
LP15A, HU	−905.9±24.7	−914.8±33.5*	−944.0±26.7*,#	<0.001a
Per high EI, %	0	32 (21.2%)	83 (66.4%)	<0.001b
Upper zone EI, %	2.51±2.35	5.82±8.27	17.91±14.68	NA
Middle zone EI, %	3.16±2.52	6.42±6.64	14.72±11.54	NA
Lower zone EI, %	2.77±2.62	6.36±7.36	15.13±13.10	NA
Emphysema distribution
ULP, n (%)	21 (16.4)	27 (17.9)	61 (48.8)	<0.001c
MHE, n (%)	84 (65.6)	70 (46.4)	37 (39.6)
LLP, n (%)	23 (18.0)	54 (35.8)	27 (21.6)

Notes: Data are presented as mean ± SD or n (%).

* P<0.01,

** P<0.05 versus controls;

# P<0.01 versus asthma patients.

a Analysis of Kruskal–Wallis test.

b Analysis of Mann–Whitney U test.

c Analysis of chi-square test.

Abbreviations: EI, emphysema index; LAA%-910, percentage of lung voxels with CT attenuation value below −910 HU; %LAA-950, percentage of lung voxels with CT attenuation value below −950 HU; LLP, lower-lung-zone predominance; LP10A, mean lung attenuation value at the 10th percentile on lung attenuation curve; LP15A, mean lung attenuation value at the 15th percentile on lung attenuation curve; MHE, middle/homogeneous distribution; NA, not available; SD, standard deviation; ULP, upper-lung-zone predominance.

Table 3 Characteristics of asthma patients with high and low EI

Characteristics	Asthma with high EI (n=32)	Asthma with low EI (n=119)	P-value
Age, years	61.3±9.4	57.4±9.3	0.046a
Sex, female/male	6/26	75/44	<0.001b
BMI, kg/m^2	22.5±3.2	26.4±3.7	<0.001a
Smoking, pack-years	29.8±30.0	7.4±16.1	<0.001a
Current/former/never smoker	11/12/9	17/11/91	<0.001b
Acute exacerbations	1.7±1.1	0.9±0.7	<0.001a
Postbronchodilator
FEV1 % predicted	49.5±16.7	69.2±22.1	<0.001a
FVC% predicted	84.3±16.4	89.8±13.4	0.097a
VC% predicted	85.9±15.9	89.8±17.4	0.133a
FEV1/FVC%	47.9±10.6	63.9±12.8	<0.001a
Response to β2 -agonist
ΔFEV1, L	0.334±0.158	0.298±0.189	0.17a
% change in FEV1 %	31.2±19.8	20.1±14.6	<0.01a
Percentage of airflow limitation	100%	60.50%	<0.001a
%LAA-950, %	17.1±6.3	3.3±2.7	<0.001a
Per ULP, %	11 (34.4)	16 (13.4)	0.006b

Notes: Data are presented as mean ± SD or n (%).

a Analysis of Mann–Whitney U test.

b Analysis of chi-square test.

Abbreviations: BMI, body mass index; EI, emphysema index; ΔFEV₁, increases in forced expiratory volume in 1 second; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; %LAA-950, percentage of lung voxels with CT attenuation value below −950 HU; SD, standard deviation; ULP, upper-lung-zone predominance; VC, vital capacity.

Table 4 Characteristics of asthma patients with high EI and COPD patients

Characteristics	Asthma with high EI (n=32)	COPD (n=125)	P-value
Age, years	61.2±9.4	65.8±9.3	0.025a
Sex, female/male	6/26	32/93	0.494b
BMI, kg/m^2	22.5±3.2	22.6±4.5	0.918a
Smoking, pack-years	29.8±30.0	34.5±26.6	0.224a
Current/former/never smoker	11/12/9	57/49/19	0.207b
Acute exacerbations	1.7±1.1	1.2±0.9	0.012a
Postbronchodilator
FEV1% predicted	49.5±16.7	44.3±18.6	0.152a
FVC% predicted	84.3±16.4	73.6±17.5	0.004a
VC% predicted	85.9±15.9	76.0±16.2	0.002a
FEV1/FVC%	47.9±10.6	48.1±12.2	0.862a
Response to β2-agonist
ΔFEV1, L	0.334±0.158	0.143±0.009	<0.001a
% change in FEV1%	31.2±19.8	15.2±12.8	<0.001a
%LAA-950, %	17.1±6.3	15.8±11.9	0.105a
Per ULP, n (%)	11 (34.4)	61 (48.8)	0.144b

Notes: Data are presented as mean ± SD.

a Analysis of Mann–Whitney U test.

b Analysis of chi-square test.

Abbreviations: BMI, body mass index; EI, emphysema index; ΔFEV₁, increases in forced expiratory volume in 1 second; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; %LAA-950, percentage of lung voxels with CT attenuation value below −950 HU; SD, standard deviation; ULP, upper-lung-zone predominance; VC, vital capacity.

Table 5 Multivariate logistic regression for predictors of high EI among asthma patients

Variable	OR	95% CI	P-value
Pack-years of smoking (per 10 pack-years)	1.405	1.13–1.75	0.003
BMI, kg/m^2	0.738	0.63–0.87	<0.001
Acute exacerbations	2.720	1.36–5.4	0.005
FEV1 % predicted (per 10% decrease)	1.428	1.08–1.89	0.013

Abbreviations: EI, emphysema index; BMI, body mass index; CI, confidence interval; FEV₁, forced expiratory volume in 1 second; OR, odds ratio.