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Table 2 Inter-item correlationsa for E-RS items and wheeze item at Day − 1 for the Overall population (N = 328)

From: Reliability, validity and responsiveness of E-RS:COPD in patients with spirometric asthma-COPD overlap

Variable Chest congested Cough Mucus when coughing Difficulty with mucus Chest discomfort Chest tight Breathless How breathless Short of breath with personal care Short of breath with indoor Short of breath with outdoor Wheeze
1. Chest congested 1 0.5 0.5 0.6 0.6 0.6 0.5 0.5 0.5 0.5 0.5 0.5
2. Cough 0.5 1 0.6 0.5 0.5 0.4 0.4 0.3 0.3 0.4 0.4 0.4
3. Mucus when coughing 0.5 0.6 1 0.5 0.3 0.2 0.2 0.2 0.3 0.3 0.2 0.3
4. Difficulty with mucus 0.6 0.5 0.5 1 0.4 0.4 0.4 0.4 0.4 0.5 0.4 0.5
5. Chest discomfort 0.6 0.5 0.3 0.4 1 0.8 0.6 0.5 0.5 0.5 0.5 0.5
6. Chest tight 0.6 0.4 0.2 0.4 0.8 1 0.6 0.5 0.5 0.5 0.5 0.5
7. Breathless 0.5 0.4 0.2 0.4 0.6 0.6 1 0.7 0.5 0.6 0.7 0.5
8. How breathless 0.5 0.3 0.2 0.4 0.5 0.5 0.7 1 0.5 0.5 0.6 0.5
9. Short of breath with personal care 0.5 0.3 0.3 0.4 0.5 0.5 0.5 0.5 1 0.7 0.6 0.4
10. Short of breath (indoor) 0.5 0.4 0.3 0.5 0.5 0.5 0.6 0.5 0.7 1 0.7 0.4
11. Short of breath (outdoor) 0.5 0.4 0.2 0.4 0.5 0.5 0.7 0.6 0.6 0.7 1 0.5
Wheeze 0.5 0.4 0.3 0.5 0.5 0.5 0.5 0.5 0.4 0.4 0.5 1
  1. aData were analyzed using Spearman’s correlation
  2. Correlations > 0.40 and > 0.70 were defined as moderate and strong, respectively
  3. E-RS Evaluating Respiratory Symptoms in chronic obstructive pulmonary disease