Table 2

Description* of the three chronic obstructive pulmonary disease (COPD) groups identified by cluster analysis

All subjects n=342Group 1 n=126Group 2 n=125Group 3 n=91F
Cough day or night, %496238448.19
Sputum day or night, %536346514.05
Asthma (self-reported), %911890.22
Dyspnoea (modified Medical Research Council scale, 0–5), mean2.
St George Respiratory Questionnaire-Symptoms (0–100), mean4954444711.35
St George Respiratory Questionnaire-Activity (0–100), mean4761324960.01
St George Respiratory Questionnaire-Impacts (0–100), mean2736172642.62
Prebronchodilator forced expiratory volume in 1 s (FEV1) (% predicted), mean49355855139.74
Postbronchodilator FEV1 (% predicted), mean52386358148.99
Postbronchodilator FEV1 to forced vital capacity ratio, mean0.530.440.570.61101.49
FEV1 bronchodilation change (% of prebronchodilator FEV1), mean9.
Thoracic gas volume (% predicted), mean13716112911452.98
Inspiratory capacity/total lung capacity ratio, mean0.310.230.340.3795.26
Carbon monoxide diffusing capacity (% predicted), mean6554737013.67
Arterial oxygen partial pressure (mm Hg), mean7470817247.39
Time with arterial oxygen saturation <90% when sleeping (%), mean192662723.88
Minimum arterial oxygen saturation during 6-minute walk test (%), mean8986929033.13
C-reactive protein in serum (mg/dl), mean0.860.990.361.378.46
Fibrinogen in serum (g/l), mean4.134.233.774.5011.40
Tumour necrosis factor in serum (pg/ml), mean0.870.880.721.051.37
Interleukin 6 in serum (pg/ml), mean1.451.521.121.815.88
Peripheral blood neutrophil count (n×109/l), mean4.624.763.945.3523.55
Skin prick test (number of positive allergens), mean0.
Body weight (kg), mean7669749087.04
Height (cm), mean1.641.621.641.6611.24
Body mass index (kg/m2), mean28.
Fat free mass index (kg/m2), mean19.618.619.321.629.53
6-Minute walk total distance (m), mean4344144664178.52
Myocardial infarction (doctor diagnosed), %1167239.40
Congestive heart failure (doctor diagnosed), %7511711.14
Left ventricle telediastolic diameter (mm), mean50.549.650.152.35.34
Ejection fraction (%), mean59.359.758.859.50.25
Tricuspid insufficiency, %586661434.63
Diabetes (doctor diagnosed), %191614326.11
Density less than −950 Hounsfield units in both lung infracarinal thin sections (%), mean142416634.03
Bronchial wall thickness extension in right inferior lobe (score 0–3), mean1.
Potentially pathogenic microorganism colonisation, %343635260.79
Interleukin 8 (×103) in sputum supernatant (pg/ml), mean10.1111.908.548.982.72
Neutrophil count in sputum (n×106/ml), mean3702502905701.59
Maximal oxygen uptake at cardiopulmonary incremental exercise test peak (% predicted), mean6253696819.93
  • * Non-standardised values of a selection of 40 out of 224 variables in figure 1, including those obtained with the variable selection procedure (bold text) and variables selected according to clinical experts' knowledge. Complete data are provided in Supplementary table 3.

  • F values correspond to the ratio of the variance of the group means (between-group variance) over the overall variance of the variable (higher values meaning higher relevance of the variable for separating cluster groups), and were obtained by means of linear regression models using each variable as the outcome, and the cluster group as the exposure (see Supplement for details).

  • Variables obtained in a subsample of patients (see text for details).