Bland and Altman plots for SGRQ, CAT, CCQ. SGRQ = St George’s Respiratory Questionnaire, CAT = COPD Assessment Test, CCQ = Clinical COPD Questionnaire. CAT scores are multiplied by 2.5(adjCAT), CCQ scores by 17.67(adjCCQ). Right Y ax shows the original scale. Orange line is the regression line. Dashed lines represent the 95% confidence interval. Straight line represents the bias.