Baseline Characteristics
The mean age of 158 subjects was 52.18±8.56 years, ranging from 40 to 76 years (Table 1). There were 123 males and 35 females. Overall, 86 (54.4%) participants were under a low risk of developing COPD and 72 were (45.5%) in the high-risk group. There was no statistical difference in BMI, smoking index, or exposure to dust between the two groups. Compared with subjects in the high-risk group, those in the low-risk group had similar scores for mMRC, CAT, and CCQ (p=0.53, p=0.47, and p=0.84, respectively). The FEV1/FVC and FEV1%prep in thte low-risk group were significantly lower than those in the high-risk group (0.82±0.07 vs. 0.79±0.08, 0.92±0.14 vs. 0.86±0.13, p<0.05), while no difference was found in FEV1 and FVC (p=0.47 and p=0.93, respectively).
Table 1
Demographics and baseline characteristics of the study subjects
Demographics and baseline characteristics
|
Low-risk group (n=86)
|
High-risk group (n=72)
|
P value
|
Age (years)
|
51.17±7.30
|
52.73±8.39
|
0.06
|
Sex
|
-
|
-
|
0.98
|
Male
|
67(77.9%)
|
56(77.8%)
|
-
|
Female
|
19(22.1%)
|
16(22.2%)
|
-
|
Height (m)
|
(1.62,1.71)
|
(1.60,1.71)
|
0.18
|
Weight (kg)
|
65.05±9.07
|
66.89±9.3
|
0.21
|
BMI (kg/m2)
|
23.70±2.99
|
23.91±2.40
|
0.63
|
Exposure to dust (former: never)
|
22:64
|
20:52
|
0.84
|
Smoking index (pack-years)
|
(0,22.5)
|
(0,28.25)
|
0.90
|
Clinical questionnaires
|
-
|
-
|
-
|
mMRC
|
0.17±0.41
|
0.22±0.54
|
0.53
|
CAT
|
3.81±4.57
|
4.36±4.74
|
0.47
|
CCQ
|
1.11±6.19
|
1.31±6.27
|
0.84
|
Spirometry
|
-
|
-
|
-
|
FEV1 (L)
|
2.71±0.67
|
2.64±0.67
|
0.47
|
FVC (L)
|
3.31±0.78
|
3.31±0.75
|
0.93
|
FEV1/FVC
|
0.82±0.07
|
0.79±0.08
|
0.01
|
FEV1%prep
|
0.92±0.14
|
0.86±0.13
|
0.01
|
Data are mean ± standard deviation or median (IQR). p values comparing low-risk group and high-risk group are from two-sample t-test, Mann-Whitney U test, χ²or Fisher’s exact test.
Comparison Of Hrct Parameters
A comparison of HRCT parameters between the two groups (low-risk group n=86, high-risk group n=72) is shown in Table 2. The mean values of LAA-950ins% in the left lung, right lung, and the entire lung were 1.80±1.73, 5.94±2.00, and 5.92±1.98 in the low-risk group, and 5.69±1.80, 6.52±2.48, and 6.36±1.70 in the high-risk group, respectively. The value of LAA-950ins%, called the emphysema index, showed a difference between two groups only in the left lung (p=0.02), but there was no difference in the right lung or the entire lung (p=0.11 and p=0.15). The mean LAA-856exp% in the left lung, right lung, and the entire lung were 14.75±5.90, 14.36±6.14, and 14.32±6.14 in the low-risk group, and 19.61±6.59, 21.54±6.78, and 21.25±6.63 in the high-risk group, respectively. The value of LAA-856exp%, called the air trapping index, was significantly higher in the high-risk group than in the low-risk group (p=0.00). The value of MLDins in the low-risk group was significantly higher than that in the high-risk group in the left lung (-751.66±29.32 vs. -765.70±38.29, p=0.01) and in the entire lung (-757.51±4.25 vs. -760.40±5.02, p=0.04). The value of MLDexp in the low-risk group was also significantly higher than that in the high-risk group in the left lung (-732.76±44.08 vs. -745.26±35.24, p=0.04), in the right lung (-738.13±36.89 vs. -754.69±30.50, p=0.00), and in the entire lung (-735.86±39.10 vs. -750.49±31.91, p=0.01).
Table 2
Comparison of HRCT parameters between the low-risk group and high-risk group
|
Low-risk group
|
High-risk group
|
P value
|
\({\mathbf{L}\mathbf{A}\mathbf{A}}_{-950\mathbf{i}\mathbf{n}\mathbf{s}}\) (ml)
|
|
|
|
Left lung
|
77.92±36.10
|
90.95±32.09
|
0.02
|
Right lung
|
90.97±39.57
|
107.04±47.34
|
0.02
|
Entire lung
|
170.08±74.94
|
195.97±70.93
|
0.03
|
\({\mathbf{L}\mathbf{V}}_{\mathbf{i}\mathbf{n}\mathbf{s}}\) (ml)
|
|
|
|
Left lung
|
1295.87±271.28
|
1412.11±277.34
|
0.02
|
Right lung
|
1494.76±320.03
|
1619.00±324.52
|
0.02
|
Entire lung
|
2806.53±600.09
|
3041.12±590.16
|
0.02
|
\({\mathbf{L}\mathbf{A}\mathbf{A}}_{-950\mathbf{i}\mathbf{n}\mathbf{s}}\)%
|
|
|
|
Left lung
|
1.80±1.73
|
5.69±1.80
|
0.02
|
Right lung
|
5.94±2.00
|
6.52±2.48
|
0.11
|
Entire lung
|
5.92±1.98
|
6.36±1.70
|
0.15
|
\({\mathbf{M}\mathbf{L}\mathbf{D}}_{\mathbf{i}\mathbf{n}\mathbf{s}}\)(HU)
|
|
|
|
Left lung
|
-751.66±29.32
|
-765.70±38.29
|
0.01
|
Right lung
|
-747.36±181.63
|
-761.52±25.28
|
0.48
|
Entire lung
|
-757.51±4.25
|
-760.40±5.02
|
0.04
|
\({\mathbf{L}\mathbf{A}\mathbf{A}}_{-856\mathbf{e}\mathbf{x}\mathbf{p}}\) (ml)
|
|
|
|
Left lung
|
162.34±118.40
|
265.90±127.46
|
0.00
|
Right lung
|
(61.57,123.62)
|
(140.49,371.61)
|
0.00
|
Entire lung
|
326.62±209.61
|
582.05±270.14
|
0.00
|
\({\mathbf{L}\mathbf{V}}_{\mathbf{e}\mathbf{x}\mathbf{p}}\) (ml)
|
|
|
|
Left lung
|
997.28±266.62
|
1191.13±275.22
|
0.00
|
Right lung
|
1103.39±366.67
|
1398.92±345.03
|
0.00
|
Entire lung
|
2104.40±561.51
|
2612.62±606.93
|
0.00
|
\({\mathbf{L}\mathbf{A}\mathbf{A}}_{-856\mathbf{e}\mathbf{x}\mathbf{p}}\mathbf{\%}\)
|
|
|
|
Left lung
|
14.75±5.90
|
19.61±6.59
|
0.00
|
Right lung
|
14.36±6.14
|
21.54±6.78
|
0.00
|
Entire lung
|
14.32±6.14
|
21.25±6.63
|
0.00
|
\({\mathbf{M}\mathbf{L}\mathbf{D}}_{\mathbf{e}\mathbf{x}\mathbf{p}}\) (HU)
|
|
|
|
Left lung
|
-732.76±44.08
|
-745.26±35.24
|
0.04
|
Right lung
|
-738.13±36.89
|
-754.69±30.50
|
0.00
|
Entire lung
|
-735.86±39.10
|
-750.49±31.91
|
0.01
|
Data are mean ± standard deviation or median (IQR). p values comparing low-risk group and high-risk group are from two-sample t-test, Mann-Whitney U test, χ²or Fisher’s exact test.
Correlations Between Quantitative Measurements And Pulmonary Function Parameters
The correlations of various quantitative HRCT parameters at suspended full inspiration with the pulmonary function test variables are shown in Table 3. The LAA-950ins% showed a strong correlation with the FEV1/FVC (r=-0.33 in the left lung, r=-0.22 in the right lung, r=-0.26 in the entire lung, p<0.05), a moderate correlation with FEV1 only in the left lung (r=-0.19, p=0.04), and no correlation with FVC or FEV1%prep. TheLAA-950ins also showed a strong correlation with the FEV1/FVC (r=-0.33 in the left lung, r=-0.22 in the right lung, r=-0.26 in the entire lung, p<0.05), but no correlation with FEV1, FVC, or FEV1%prep. TheLVins showed a statistical correlation with FVC (r=0.23 in the left lung, r=0.19 in the right lung, r=0.21 in the entire lung, p<0.05), but no correlation with FEV1, FEV1/FVC, or FEV1%prep. The MLDins in the left lung and in the entire lung showed a correlation with the FEV1/FVC (r=0.20 in the left lung and r=0.21 in the entire lung, p<0.05), but the MLDins in the right lung had no correlation with the FEV1/FVC (p=0.06). There was no statistical correlation between the MLDins and three other physiologic parameters, including FEV1, FVC, and FEV1%prep (p>0.05).
Table 3
The correlation between quantitative HRCT parameters at inspiration and pulmonary function parameters
|
|
\({\text{F}\text{E}\text{V}}_{1}\)
|
FVC
|
\({\text{F}\text{E}\text{V}}_{1}\)/FVC
|
\({\text{F}\text{E}\text{V}}_{1}\text{\%}\)prep
|
|
|
r
|
P
|
R
|
P
|
r
|
P
|
r
|
P
|
Left lung
|
\({\text{L}\text{A}\text{A}}_{-950\text{i}\text{n}\text{s}}\)
|
-0.07
|
0.46
|
0.02
|
0.80
|
-0.33**
|
0.00
|
-0.12
|
0.19
|
\({\text{L}\text{V}}_{\text{i}\text{n}\text{s}}\)
|
0.16
|
0.09
|
0.23*
|
0.01
|
-0.23*
|
0.01
|
-0.07
|
0.47
|
\({\text{L}\text{A}\text{A}}_{-950\text{i}\text{n}\text{s}}\)%
|
-0.19*
|
0.04
|
-0.11
|
0.26
|
-0.33**
|
0.00
|
-0.12
|
0.18
|
\({MLD}_{ins}\)
|
0.07
|
0.48
|
0.01
|
0.91
|
0.20*
|
0.03
|
0.05
|
0.57
|
Right lung
|
\({\text{L}\text{A}\text{A}}_{-950\text{i}\text{n}\text{s}}\)
|
-0.02
|
0.81
|
0.05
|
0.60
|
-0.22*
|
0.02
|
-0.09
|
0.35
|
\({\text{L}\text{V}}_{\text{i}\text{n}\text{s}}\)
|
0.15
|
0.12
|
0.19*
|
0.04
|
-0.12
|
0.18
|
-0.08
|
0.42
|
\({\text{L}\text{A}\text{A}}_{-950\text{i}\text{n}\text{s}}\)%
|
-0.15
|
0.12
|
-0.08
|
0.42
|
-0.22*
|
0.02
|
-0.09
|
0.35
|
\({MLD}_{ins}\)
|
0.02
|
0.84
|
-0.03
|
0.76
|
0.17
|
0.06
|
0.02
|
0.81
|
Entire lung
|
\({\text{L}\text{A}\text{A}}_{-950\text{i}\text{n}\text{s}}\)
|
0.00
|
0.99
|
0.08
|
0.39
|
-0.26**
|
0.01
|
-0.09
|
0.34
|
\({\text{L}\text{V}}_{\text{i}\text{n}\text{s}}\)
|
0.15
|
0.10
|
0.21*
|
0.02
|
-0.18
|
0.05
|
-0.08
|
0.40
|
\({\text{L}\text{A}\text{A}}_{-950\text{i}\text{n}\text{s}}\)%
|
-0.12
|
0.20
|
-0.05
|
0.63
|
-0.26**
|
0.01
|
-0.11
|
0.26
|
|
\({MLD}_{ins}\)
|
0.07
|
0.45
|
0.01
|
0.94
|
0.21*
|
0.02
|
0.05
|
0.57
|
** p<0.01, * p<0.05
The LAA-856exp% showed a significantly strong correlation with FEV1, FEV1/FVC, and FEV1%prep (p<0.05) in Table 4. Among them, the most optimal correlation between LAA-856exp% was found with FEV1/FVC (r=-0.33 in the left lung, r=-0.23 in the right lung, and r=-0.28 in the entire lung). No useful correlation was found between the LAA-856exp% and FVC. Both LAA-856exp and LVexp showed statistical correlation with FEV1/FVC (r=-0.32 in the left lung, r=-0.23 in the right lung, r=-0.28 in the entire lung, and r=-0.29 in the left lung, r=-0.17 in the right lung, r=-0.25 in the entire lung, respectively, p<0.05). The LAA-856exp% and LVexp also showed correlation with FEV1%prep (r=-0.24 in the left lung, r=-0.26 in the right lung, r=-0.25 in the entire lung and r=-0.25 in the left lung, r=-0.24 in the right lung, r=-0.27 in the entire lung, respectively, p<0.05), but neither of them correlated with FEV1or FVC. For the MLDexp, strong and positive correlations were found with FEV1/FVC (r=0.31 in the left lung, r=0.25 in the right lung and r=0.29 in the entire lung, p<0.01), while no statistical correlation was found with FEV1, FVC, and FEV1%prep (p>0.05).
Table 4
The correlation between quantitative HRCT parameters at expiration and pulmonary function parameters
|
|
\({\text{F}\text{E}\text{V}}_{1}\)
|
FVC
|
\({\text{F}\text{E}\text{V}}_{1}\)/FVC
|
\({\text{F}\text{E}\text{V}}_{1}\%\)prep
|
|
|
r
|
P
|
R
|
P
|
r
|
P
|
r
|
P
|
Left lung
|
\({\text{L}\text{A}\text{A}}_{-856\text{e}\text{x}\text{p}}\)
|
-0.13
|
0.14
|
-0.09
|
0.34
|
-0.32**
|
0.00
|
-0.24**
|
0.01
|
\({\text{L}\text{V}}_{\text{e}\text{x}\text{p}}\)
|
-0.06
|
0.52
|
-0.01
|
0.92
|
-0.29**
|
0.01
|
-0.25**
|
0.01
|
\({\text{L}\text{A}\text{A}}_{-856\text{e}\text{x}\text{p}\text{\%}}\)
|
-0.19*
|
0.04
|
-0.15
|
0.11
|
-0.33**
|
0.00
|
-0.24**
|
0.01
|
\({MLD}_{exp}\)
|
-0.06
|
0.50
|
-0.14
|
0.13
|
0.31**
|
0.00
|
0.03
|
0.73
|
Right lung
|
\({\text{L}\text{A}\text{A}}_{-856\text{e}\text{x}\text{p}}\)
|
-0.16
|
0.08
|
-0.13
|
0.16
|
-0.23*
|
0.01
|
-0.26**
|
0.00
|
\({\text{L}\text{V}}_{\text{e}\text{x}\text{p}}\)
|
-0.08
|
0.38
|
-0.06
|
0.50
|
-0.17*
|
0.03
|
-0.24*
|
0.01
|
\({\text{L}\text{A}\text{A}}_{-856\text{e}\text{x}\text{p}\text{\%}}\)
|
-0.20*
|
0.03
|
-0.17
|
0.08
|
-0.23*
|
0.01
|
-0.25**
|
0.01
|
\({MLD}_{exp}\)
|
-0.06
|
0.49
|
-0.13
|
0.15
|
0.25**
|
0.00
|
0.04
|
0.69
|
Entire lung
|
\({\text{L}\text{A}\text{A}}_{-856\text{e}\text{x}\text{p}}\)
|
-0.14
|
0.14
|
-0.10
|
0.29
|
-0.28**
|
0.00
|
-0.25**
|
0.01
|
\({\text{L}\text{V}}_{\text{e}\text{x}\text{p}}\)
|
-0.09
|
0.34
|
-0.05
|
0.59
|
-0.25**
|
0.01
|
-0.27**
|
0.00
|
\({\text{L}\text{A}\text{A}}_{-856\text{e}\text{x}\text{p}\text{\%}}\)
|
-0.20*
|
0.03
|
-0.16
|
0.08
|
-0.28**
|
0.00
|
-0.24**
|
0.01
|
\({MLD}_{exp}\)
|
-0.08
|
0.41
|
-0.15
|
0.10
|
0.29**
|
0.00
|
0.02
|
0.80
|
** p<0.01, * p<0.05