Table VI.
Quantitative CT indices of asthma phenotypes
| Asthma cluster 1: Severe air trapping, bronchial wall thickening, and bronchial lumen dilatation (n = 11) | Asthma cluster 2: Moderate air trapping (n = 34) | Asthma cluster 3: Severe air trapping and bronchial lumen narrowing (n = 17) | Significance (P value) | |
|---|---|---|---|---|
| Proximal airway dimensions (inspiratory) | ||||
| RB1 % wall volume | 58.1 (2.7) | 62.0 (2.6) | 64.8 (3.0) | <.005*†‡ |
| RB1 wall area/BSA (mm2/m2) | 25.0 (3.3) | 19.2 (2.5) | 12.3 (3.2) | <.005*†‡ |
| RB1 lumen area/BSA (mm2/m2) | 18.0 (2.0) | 11.7 (1.7) | 6.7 (1.7) | <.005*†‡ |
| RB1 total area/BSA (mm2/m2) | 42.9 (4.9) | 30.9 (3.8) | 18.9 (4.8) | <.005*†‡ |
| RB1 length (mm) | 11.6 (2.6) | 12.5 (2.5) | 13.5 (2.8) | .2 |
| RB1 wall volume (mm3) | 540.5 (92.8) | 453.1 (120.4) | 324.2 (102.9) | <.005†‡ |
| RB1 wall volume (% greater than upper 95% CI of healthy control subjects) | 27 | 15 | 6 | .3 |
| RB1 LV (mm3) | 392.2 (78.6) | 278.0 (78.0) | 176.1 (54.0) | <.005*†‡ |
| RB1 LV (% less than lower 95% CI of healthy control subjects) | 9 | 65 | 94 | <.005 |
| RB1 total volume (mm3) | 932.7 (163.3) | 731.2 (194.8) | 500.3 (154.4) | <.005*†‡ |
| Pi10 wall area (mm2) | 16.9 (1.9) | 16.2 (1.7) | 16.2 (1.4) | .5 |
| Po20 % wall area | 64.7 (2.5) | 64.8 (2.3) | 65.5 (2.5) | .6 |
| Air trapping | ||||
| Expiratory VI −850 (%) | 23.7 (16.0) | 17.2 (11.9) | 24.8 (13.9) | .1 |
| Expiratory VI −850 (% greater than upper 95% CI of healthy control subjects) | 64 | 29 | 59 | .045 |
| VI−850/−950 E-I (%) | −28.6 (12.8) | −31.7 (13.5) | −27.6 (11.4) | .5 |
| VI−850 E-I (%) | −35.9 (14.2) | −39.9 (15.5) | −38.3 (12.2) | .7 |
| MLD E/I | 0.876 (0.06) | 0.857 (0.06) | 0.864 (0.05) | .6 |
| MLD E/I (% greater than upper 95% CI of healthy control subjects) | 73 | 53 | 65 | .5 |
| Fractal dimension | ||||
| Inspiratory Dav | 1.712 (0.04) | 1.686 (0.04) | 1.671 (0.04) | .04† |
| Inspiratory Dav (% less than lower 95% CI of healthy control subjects) | 46 | 65 | 77 | .2 |
| Expiratory LAC-D −850 | 1.838 (0.09) | 1.814 (0.1) | 1.794 (0.05) | .4 |
Data are expressed as means (SDs).
LAC-D −850, Fractal dimension of low attenuation cluster at a threshold of −850 HU.
Intergroup comparisons
One-way ANOVA with the Tukey test to compare all pairs of columns: *P < .05, asthma cluster 1 versus asthma cluster 2; †P < .05, asthma cluster 1 versus asthma cluster 3; and ‡P < .05, asthma cluster 2 versus asthma cluster 3.