Exploring the optimum approach to the use of CT densitometry in a randomised placebo-controlled study of augmentation therapy in alpha 1-antitrypsin deficiency

Table 3 Sensitivity ratios for the different CT densitometric parameters (whole lung; analysis of covariance model)^a

	Model with lung volume adjustment
Outcome measure	LS mean change from baseline	Standard error	Sensitivity index^b	F-test^c
PD15 (g/L)	-4.12	0.539	7.64	-
MLD (g/L)	-3.31	0.801	4.14	< 0.05
VI-910 (%)	2.25	0.517	4.36	< 0.05
VI-950 (%)	2.36	0.420	5.61	NS
	Model without lung volume adjustment
Outcome measure	LS mean change from baseline	Standard error	Sensitivity index^b	Reduction in sensitivity index^d
PD15 (g/L)	-4.24	0.771	5.50	2.14
MLD (g/L)	-3.49	1.221	2.86	1.28
VI-910 (%)	2.34	0.687	3.41	0.95
VI-950 (%)	2.41	0.514	4.69	0.92

LS mean, least squares mean; PD15, 15th percentile lung density; MLD, mean lung density;
VI-910, voxel index at a threshold of -910 (measured in %); VI-950, voxel index at a threshold of -950 (measured in %); NS, not significant. ^aResults based on estimates from endpoint analysis for placebo group only. ^bRatio of absolute value of mean change divided by standard error. ^cRatio of outcome measure as compared to PD15. ^dSensitivity index from model with lung volume adjustment minus sensitivity index from model without lung volume adjustment.

ISSN: 1465-993X