Is the COPD assessment test (CAT) effective in demonstrating the systemic inflammation and other components in COPD?

Chronic obstructive pulmonary disease (COPD) is currently a complex, multicomponent disorder. The COPD Assessment Test (CAT) has been increasingly used to assess COPD patients. This study aims to investigate the relationship between CAT and inflammation markers and other COPD components.

We enrolled 110 stable COPD patients and 65 control subjects in this study. All patients completed the CAT questionnaire and the modified Medical Research Council (mMRC) dispnea scale. The quality of life of these patients was measured with St. George's Respiratory Questionnaire (SGRQ). Levels of TNFα, IL-6, CRP were determined in blood samples.

In COPD patients, serum levels of TNFα (109.5 ± 58 pg/ml), IL-6 (10.3 ± 18 pg/ml), and C-reactive protein (CRP) (1.6 ± 1.7 mg/L) were found to be significantly higher compared to controls (TNF-α: 14.6 ± 18 pg/ml, IL-6: 2.14 ± 1.9 pg/ml, CRP: 0.4 ± 0.3mg/L, p<0.001). These markers were correlated with smoking (r from 0.27 to 0.35, p<0.001), FEV1 (r from -0.39 to -0.57, p<0.001), FVC (r from -0.32 to -0.37, p<0.001) and FEV1/FVC (r from -0.31 to -0.66, p<0.001). The CAT score correlated with GOLD spirometric stages, mMRC dyspnea score, number of exacerbations in the previous year and FEV1 (p<0.001). There was a significant correlation between levels of CRP and the CAT score (r=0.43, p<0.001) but no similar relationship between levels of TNFα and IL-6 and the CAT was observed.

Systemic inflammation persists in the stable period of COPD. CRP, one of the inflammation markers, was correlated with the CAT. Further studies are required to confirm the relationship between CAT and biomarkers.