Table 2.

—Automated Airway Counts and LAD (%) by Study Group

Automated CT Scan Measure	CF	Disease Control	P Value
Inspiratory airway counta
Inspiratory slices per scan, No.	16.1 (3.2)	15.9 (2.4)	.82
Total	13.2 (6.5)	7.0 (2.6)	< .0001
Central	11.4 (4.7)	6.6 (2.2)	< .0001
Peripheral	1.8 (2.0)	0.4 (0.5)	.0003
Expiratory LAD (%)b
Total	11.4 (10.6)	4.2 (2.6)	< .001
Upper lung zone	15.0 (15.6)	3.7 (4.6)	< .001
Middle lung zone	9.4 (9.9)	3.1 (2.7)	.002
Lower lung zone	11.3 (10.6)	5.5 (3.5)	.008
Expiratory fixed (%)c
Total	11.4 (10.4)	4.0 (2.4)	< .001
Upper lung zone	14.7 (15.0)	2.6 (2.6)	< .0001
Middle lung zone	9.1 (9.2)	3.3 (2.6)	.002
Lower lung zone	11.8 (11.0)	5.5 (3.3)	.004

Data are presented as mean (SD). HRCT = high-resolution CT; LAD = low attenuation density. See Table 1 legend for expansion of other abbreviation.

^aCF: n = 35; disease control: n = 12. The number of visible airways (total, central, and peripheral) averaged over all inspiratory HRCT scan slices in an individual.

^bCF: n = 34; disease control: n = 12. Total LAD (%) averaged over six expiratory HRCT scan slices in an individual subject. Upper lung zones are composed of expiratory scan levels 1 and 2; middle lung zones are expiratory scan levels 3 and 4; and lower lung zones are expiratory scan levels 5 and 6.

^cCF: n = 34; disease control: n = 12. Air trapping score calculated using fixed −850 Hounsfield unit threshold.