Table 2

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

Training sampleValidation sample
C1: meanC2: meanC3: meanC4: meanC1: meanC2: meanC3: meanC4: mean
Gender, % female0.440.530.520.400.430.510.530.40
Race, % African-American0.300.460.370.190.290.450.370.17
FEV1, per cent of predicted95.381.974.941.295.781.673.842.0
Pack years38.045.842.856.838.346.943.155.9
Emphysema at −950HU2.63.31.320.
Segmental airway wall thickness58.861.564.162.758.861.464.263.0
Upper/lower emphysema ratio0.
Upper/lower emphysema difference−0.31.4−0.32.6−0.31.7−0.32.9
Gas trapping†12.916.513.452.113.117.313.352.7
  • 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.