Table 2

Cluster characteristics in training and validation data for core feature set cluster solution, k=4

	Training sample				Validation sample
	C1: mean	C2: mean	C3: mean	C4: mean	C1: mean	C2: mean	C3: mean	C4: mean
N	1598	623	1122	844	1595	620	1060	826
Age	58.9	58.0*	56.8	65.4	58.7	58.9*	57.3	65.4
Gender, % female	0.44	0.53	0.52	0.40	0.43	0.51	0.53	0.40
Race, % African-American	0.30	0.46	0.37	0.19	0.29	0.45	0.37	0.17
FEV₁, per cent of predicted	95.3	81.9	74.9	41.2	95.7	81.6	73.8	42.0
FEV₁/FVC	0.76	0.70	0.71	0.42	0.76	0.69	0.71	0.42
BMI	28.7	27.9	31.4*	26.7	28.3	27.6	32.0*	26.8
Pack years	38.0	45.8	42.8	56.8	38.3	46.9	43.1	55.9
Emphysema at −950HU	2.6	3.3	1.3	20.5	2.7	3.6	1.4	20.7
Segmental airway wall thickness	58.8	61.5	64.1	62.7	58.8	61.4	64.2	63.0
Upper/lower emphysema ratio	0.7	6.7	0.6	2.2	0.7	8.3	0.6	2.3
Upper/lower emphysema difference	−0.3	1.4	−0.3	2.6	−0.3	1.7	−0.3	2.9
Gas trapping†	12.9	16.5	13.4	52.1	13.1	17.3	13.3	52.7

Values represent the mean of each variable for each cluster unless otherwise specified.
Only the variables shown in bold were used as input variables for the primary clustering solution (CF4).
*p Value comparing mean in training to validation <0.05 for t test.
†%LAA using −856 Hounsfield unit threshold on expiratory CT scan.
C1, relatively resistant smokers; C2, mild upper zone-predominant emphysema; C3, airway-predominant; C4, severe emphysema.