Alternative definitions of chronic bronchitis and their correlation with CT parameters

Phenotyping of chronic bronchitis (CB) using COPD assessment tool (CAT) scores and St George's Respiratory Questionnaire (SGRQ) has rarely been attempted. The present study defined CB using CAT 1 and 2 scores and the questions on the severity of cough and sputum from the SGRQ. Furthermore, the predictability of CT parameters was also assessed for each CB definition.

Patients enrolled in the Korean Obstructive Lung Disease study from June 2005 to October 2015 were evaluated for this study. The patients were spirometrically diagnosed with COPD and had a smoking history of >10 pack-years. Volumetric CT scans were performed for each patient upon enrollment in the cohort. Two definitions of CB using CAT 1/2 scores and SGRQ questions were used to phenotype CB among the study patients. Receiver operating characteristic curve analysis was performed to estimate the predictability of CT parameters for the CB phenotypes.

Using CAT 1/2 scores, 57 of 279 (20.4%) patients had CB, and 178 of 573 (31.1%) had CB when the SGRQ questions were used to phenotype it. Total CAT and SGRQ scores were significantly higher in the CB group than those in the non-CB group for both definitions of CB. Forced expiratory volume in 1 second was lower for both CAT-defined and SGRQ-defined CB than that in the non-CB group. Mean wall thickness was significantly higher for both CB groups than in the non-CB group. Expiratory lung volume was higher and mean lung density was significantly lower for the SGRQ-defined CB group than non-CB group.

The 2 CB definitions using CAT scores and the SGRQ questions correlated with associated CT airway parameters. SGRQ-defined CB better reflected the accompaniment of small airway obstruction when compared with CAT-defined CB.