Comparison of bronchodilator responsiveness (BDR) between GINA guidelines and ERS/ATS 2021 interpretative strategies

<bold>Introduction:</bold> BDR testing is a pivotal aspect of evaluating respiratory function. According to GINA guidelines BDR is expressed as the absolute and relative change of FEV1 from baseline values. The 2021 ERS/ATS strategies (ERS/ATS 2021) recommend changes of FEV1 or FVC to the percentage relative to the predicted values rather than baseline. <bold>Aim:</bold> To study the concordance and discordance of the BDR calculated using the GINA guidelines and ERS/ATS 2021. <bold>Methods:</bold> Retrospective study conducted in tertiary care pulmonary service in India. Adult patients who were referred to the pulmonary function lab from Sept-Dec, 2023 for the first time, with clinical diagnosis of obstructive airway diseases were included. Indian population specific reference standards were used to derive the predicted values. Positive BDR(BDR+) as per GINA guidelines: >12% and >200 ml in FEV1 from baseline, and as per 2021 stg: >10% of predicted value in FEV1 or FVC. <bold>Results:</bold> This study analyzed data from 2126 patients (57.6% males, mean age − 46.3). BDR+ was observed in 19.1% as per the GINA and 23.4% as per ERS/ATS 2021. ~ 24% of patients with BDR+ in 2021 were diagnosed as BDR- by GINA. Concordance was seen in 1975(92.8 %) patients; Kappa-0.789 (p <0.05) and this was maintained across subgroups. Better agreement was seen in asthma than COPD (0.81 vs 0.59;p<0.05), in those with obstruction than no obstruction (0.76 vs 0.71;p<0.05). 20-29 age group had best agreement (0.89;p<0.05), agreement reduced with increasing in age. <bold>Conclusion:</bold> Our study shows that there is substantial agreement between the GINA guidelines and 2021 ERS/ATS strategies, however GINA missed BDR(+) in ~ 24%.