Cross sectional and longitudinal analysis of the relationship between the COPD assessment test (CAT), multi detector-row CT and pulmonary function test

Backgound: The 2011 GOLD guidelines describe that we have to measure not only pulmonary function tests (PFTs) but also health status for evaluating COPD patients. COPD Assessment Test (CAT), which is used worldwide to evaluate health status in COPD patients, is one of the factors in combined assessment of COPD such as category A (C) or B (D) in the 2011 GOLD guidelines. However, little is known about the difference between category A (C) and B (D) in radiological findings and/or pulmonary functions. The aim of this study is to evaluate the relationship between CAT, multi detector-row CT (MDCT) and PFTs. Methods : One hundred seventy patients were enrolled. They underwent CAT, PFTs and MDCT at baseline and after 1-year follow up. We defined emphysema-type as their low attenuation volume percentage (LAV%) obtained by CT more than 10%. We evaluated the relationships between CAT, PFTs and MDCT. Results : Inverse weak correlations were observed between CAT and FEV 1 (r = -0.30), FEV 1 % predicted (r = -0.32) and %DLCO/VA (r = -0.36), respectively. CAT scores were significantly higher in emphysema-type (LAV% > 10%) than in non-emphysema-type (LAV% < 3%) (p = 0.03). However, the change in CAT did not correlate with the change in FEV 1 nor %DLCO/VA. Compared to category A, %DLCO/VA in category B was significantly lower (p = 0.03), and RV/TLC in category B was significantly higher (p = 0.02). In addition, FEV 1 in category A improved by tiotropium than that in category B (p = 0.02). Conclusions : CAT is useful to evaluate clinical conditions of COPD patients. This study indicates that the difference between category A and B might be that of %DLCO/VA.