Table 3

Densitometric progression adjusted for lung volume using linear regression

Variable
Linear regression models
Intercept, mean ± SE (95% CI)
t
p value
Annual change

WL Perc15
ΔPCP = -12.12*ΔCTVol -3.57
-3.57 ± 0.83 (-5.48, -1.65)
-3.72
0.0004
-1.79
WL VI-950
ΔVI-950 = 2.54* ΔCTVol + 1.94
1.94 ± 0.44 (1.07, 2.81)
4.45
< 0.0001
0.97
WL VI-910
ΔVI-910 = 6.58* ΔCTVol + 2.28
2.28 ± 0.57 (1.15, 3.42)
4.01
0.0002
1.14

WL, whole lung; Perc15, 15th percentile point (measured in Hounsfield Units); VI-950, voxel index at a threshold of -950HU (measured in %); VI-910, voxel index at a threshold of -910HU (measured in %); Δ, change over study period; SE, standard error; 95% CI, 95% confidence interval; annual change, change outcome measure from baseline to follow-up incorporating adjustment for lung volume, estimated from the intercept (ΔCTVol = 0).

Parr et al. Respiratory Research 2008 9:21   doi:10.1186/1465-9921-9-21