TABLE 2

Exploratory factor analysis using principal components factoring

AsthmaAsthma+COPDCOPDTotal sample
Patients5105105101530
Factor loadings for RSQ items
 1#0.8000.8190.7980.812
 20.7600.7610.7340.758
 3+0.8140.8200.8060.817
 4§0.8170.7570.7440.770
Eigenvaluesƒ
 Factor 12.552.492.382.49
 Factor 20.550.570.600.55
Variance explained %63.762.459.462.4

Data are presented as n, unless otherwise stated. COPD: chronic obstructive pulmonary disease; RSQ: Respiratory Symptoms Questionnaire. #: question 1 (“In the past 4 weeks, how often have you had shortness of breath, wheezing, coughing and/or chest tightness during the day?”); : question 2 (“In the past 4 weeks, how often did you use a rescue inhaler (quick relief inhaler) in response to shortness of breath, wheezing, coughing and/or chest tightness?”); +: question 3 (“In the past 4 weeks, how limited were your activities as a result of shortness of breath, wheezing, coughing and/or chest tightness?”); §: question 4 (“In the past 4 weeks, how often did you wake up at night due to shortness of breath, wheezing, coughing and/or chest tightness?”); ƒ: one factor was retained for each analysis based on a factor retention criteria of eigenvalue ≥1.00 (a second factor did not meet this threshold and there were no items with split loadings in a two-factor solution).