Table 4  Correlation analysis between DD and chest CT in the same period.
The different stages of CT  DD
<0.55  0.55-1.10  >1.10  Total
CT1
 Normal  3  0  2  5
 Mild  16  1  4  21
 Progressive  29  10  16  55
 Severe  17  4  13  34
 Total  65  15  35  115
 χ2, P   χ 2 = 6.514   P > 0.05
 r, P   r = 0.152   P > 0.05
CT2
 Normal  1  0  0  1
 Mild  6  7  4  17
 Progressive  16  14  23  53
 Severe  1  2  23  26
 Total  24  23  50  97
 χ2, P   χ 2 = 24.340   P < 0.01
 r, P   r = 0.498   P < 0.01
CT3
 Normal  0  0  0  0
 Mild  19  10  4  33
 Progressive  10  4  13  27
 Severe  1  2  5  8
 Total  30  16  22  68
 χ2, P   χ 2 = 13.501   P < 0.01
 r, P   r = 0.423   P < 0.01