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Table 2 Minimal Clinically Important Difference (MCID) for the Clinical COPD Questionnaire (CCQ) by patient referencing. Differences between CCQ scores for Days 1 and 3 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 3
  Mean ± SD 95% confidence interval p value
GRC +1 (n = 4)    
Total 0.05 ± 0.49 -0.73, 0.83 0.852
Symptoms 0 ± 1.02 -1.62, 1.62 1.0
Function 0 ± 1.02 -1.62, 1.62 1.0
Mental 0.25§   0.414
GRC +2 to +3 (n = 20)    
Total 0.44 ± 0.66 0.13, 0.75 0.008*
Symptoms 0.74 ± 0.93 0.30, 1.17 0.002*
Function 0.26 ± 0.995 -0.20, 0.72 0.253
Mental 0.25§   0.398
GRC +4 to +5 (n = 20)    
Total 1.36 ± 1.07 0.86, 1.86 <0.001*
Symptoms 1.46 ± 0.99 1.0, 1.92 <0.001*
Function 1.31 ± 1.65 0.54, 2.08 0.002*
Mental 1.75§   0.023*
GRC +6 to +7 (n = 4)    
Total 1.95 ± 0.87 0.56, 3.34 0.021*
Symptoms 2.37 ± 1.13 0.58, 4.17 0.024*
Function 2.31 ± 0.90 0.88, 3.74 0.014*
Mental -0.25§   0.655
  1. * Statistically significant (2-tailed): p < 0.05. § Difference in median scores
  2. COPD = chronic obstructive pulmonary disease; SD = standard deviation.