B102-07 Predictive Validity of Three Definitions of Chronic Bronchitis (Mrc, Sgrq and Cat) in COPD

Abstract Rationale Three definitions of chronic bronchitis (CB) are in widespread use, the original Medical Research Council (MRC) definition (often referred to as the classic definition), with a recall period of 2 years, and those using items from the St. Georges Respiratory Questionnaire (SGRQ), with recall period the previous 4 weeks, and the COPD Assessment Test (CAT), with no recall period. A previous cross-sectional analysis showed that all three definitions were associated with comparable clinical outcomes, although not in the same patients (Wang et al. ERS 2025). This analysis aimed to compare the predictive validity of these three CB definitions in terms of future risk of exacerbations and decline in FEV1 (ΔFEV1). Methods Data were obtained from the COMPASS cohort study in China (Liang et al. ERJ Open Res. 2021;7:00201). All analyses were performed after adjusting for age, sex, smoking pack-years and baseline post-bronchodilator FEV1% predicted. To minimize the impact of any study effect, ΔFEV1 (calculated using a mixed-effects linear model), and moderate-to-severe exacerbations (rate calculated using negative binomial model) were measured over a 2-year period starting 6 months after the baseline. Results At baseline, 1696 COPD patients (mean age 65.4 years, mean post-bronchodilator FEV1 67% predicted) were enrolled. The numbers of CB positive (CB+) participants by each definition are shown in the Table 1. More patients were identified as CB+ using the MRC definition (66.2%) than either CAT (33.7%) or SGRQ (50.8%). All three definitions predicted future risk of exacerbations, but the MRC definition was the best, the CB+ patients using this definition were nearly twice as likely to have a moderate-to-severe exacerbation over 2 years than CB- (rate ratio 1.92, p0.001). Only the MRC definition identified CB+ patients who’s post-bronchodilator FEV1 was more likely to decline faster than CB- patients (difference -42.4ml/y, p=0.007). Conclusions Among the three definitions, the classic MRC definition was better at identifying patients at highest risk of moderate-to-severe exacerbations and was the only one that identified those with accelerated FEV1 decline. It appears to be a more reliable chronic bronchitis predictor of poor clinical outcomes in COPD than either CAT or SGRQ methods, possibly due to its longer recall period. Funding GSK (208630). This abstract is funded by: GSK (208630)