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Table 1 Minimal Clinically Important Difference (MCID) for the Clinical COPD Questionnaire (CCQ) by patient referencing. Differences between CCQ scores for Days 1 and 2 grouped according to Global Rating of Change (GRC) as scored by patients on a scale of -7 to 7. Note that paired-sample t-tests were used for total CCQ scores and for symptom and functional domains; Wilcoxon signed rank test was used for the mental domain.

From: Health status measurement in COPD: the minimal clinically important difference of the clinical COPD questionnaire

CCQ score category Score difference: Day 1 minus Day 2
  Mean ± SD 95% confidence interval p value
GRC +1 (n = 3)    
Total 0.30 ± 0.30 -0.45, 1.05 0.225
Symptoms -0.25 ± 1.64 -4.32, 3.82 0.816
Function 1.17 ± 0.80 -0.83, 3.16 0.128
Mental -0.5§   0.157
GRC +2 to +3 (n = 15)    
Total 0.40 ± 0.90 -0.09, 0.91 0.098
Symptoms 0.70 ± 1.09 0.98, 1.30 0.026*
Function 0.17 ± 1.37 -0.93, 0.59 0.645
Mental 1.0§   0.007*
GRC +4 to +5 (n = 14)    
Total 1.31 ± 1.09 0.69, 1.94 0.001*
Symptoms 1.13 ± 1.52 0.25, 2.0 0.016*
Function 1.48 ± 1.25 0.76, 2.20 0.001*
Mental 0.5§   0.018*
GRC +6 to +7 (n = 2)    
Total 1.95 ± 0.07 1.31, 2.59 0.016*
Symptoms 2.75 ± 1.77 -13.13, 18.63 0.272
Function 1.50 ± 1.06 -8.03, 11.03 0.295
Mental 1.25§   0.317
  1. * Statistically significant (2-tailed): p < 0.05. § Difference in median scores
  2. COPD = chronic obstructive pulmonary disease; SD = standard deviation.