Discrepancies between modified Medical Research Council dyspnea score and COPD assessment test score in patients with COPD

Background and objective: According to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines, either a modified Medical Research Council (mMRC) dyspnea score of >2 or a chronic obstructive pulmonary disease (COPD) assessment test (CAT) score of >= 10 is considered to represent COPD patients who are more symptomatic. We aimed to identify the ideal CAT score that exhibits minimal discrepancy with the mMRC score. Methods: A receiver operating characteristic curve of the CAT score was generated for an mMRC scores of 1 and 2. A concordance analysis was applied to quantify the association between the frequencies of patients categorized into GOLD groups A-D using symptom cutoff points. A kappa-coefficient was calculated. Results: For an mMRC score of 2, a CAT score of 15 showed the maximum value of Youden's index with a sensitivity and specificity of 0.70 and 0.66, respectively (area under the receiver operating characteristic curve [AUC] 0.74; 95% confidence interval [CI], 0.70-0.77). For an mMRC score of 1, a CAT score of 10 showed the maximum value of Youden's index with a sensitivity and specificity of 0.77 and 0.65, respectively (AUC 0.77; 95% CI, 0.72-0.83). The kappa value for concordance was highest between an mMRC score of 1 and a CAT score of 10 (0.66), followed by an mMRC score of 2 and a CAT score of 15 (0.56), an mMRC score of 2 and a CAT score of 10 (0.47), and an mMRC score of 1 and a CAT score of 15 (0.43). Conclusion: A CAT score of 10 was most concordant with an mMRC score of 1 when classifying patients with COPD into GOLD groups A-D. However, a discrepancy remains between the CAT and mMRC scoring systems.