Prevalence of Bronchodilator Responsiveness: A Comparison of Old Versus New Criteria

BACKGROUND: In 2021, the European Respiratory Society (ERS)/American Thoracic Society (ATS) guidelines issued a new definition of bronchodilator responsiveness, which is now defined as an increase in FEV1 or FVC by >= 10% of the predicted FEV1 or FVC. The impact of this revised definition on bronchodilator responsiveness prevalence has been relatively understudied. METHODS: We retrospectively analyzed data from 2,696 subjects who performed pulmonary function testing at the University of Iowa from 1997 to 2018. We compared the prevalence of bronchodilator responsiveness by using the 2005 (FEV1 or FVC increase >= 12% baseline value and >= 200 mL) and 2021 (FEV1 or FVC increase >= 200 mL and >= 12% of baseline value) ERS/ATS definitions, across several different respiratory diagnosis categories. We compared the prevalence of bronchodilator responsiveness using the 2 definitions by applying the McNemar test and assessed concordance of bronchodilator responsiveness by calculating kappa coefficients for the whole study population and within each diagnosis category. RESULTS: The prevalence of bronchodilator responsiveness increased from 9% when using the 2005 ERS/ATS definition to 16% when using the 2021 definition within the entire cohort and also within each respiratory diagnosis category. In the subjects with normal pre-bronchodilator spirometry, there was a low prevalence of bronchodilator responsiveness (3%) when using the 2005 definition, and the prevalence increased (8%) when using the 2021 definition. In the subjects with normal pre-bronchodilator spirometry and FEV1 Z score >= 0, 2% had bronchodilator responsivness according to the 2005 guidelines, whereas 7% had bronchodilator responsiveness according to the 2021 guidelines. CONCLUSIONS: The prevalence of bronchodilator responsiveness increased when using the new 2021 ERS/ATS definition compared with the 2005 definition. In the subjects with normal pre-bronchodilator spirometry, the prevalence of bronchodilator responsiveness increased when using the 2021 definition, in particular, among those with an FEV1 Z score >= 0, which raises concerns for overdiagnosis. Future investigations should examine the correlation of bronchodilator responsiveness with clinical outcomes in this group of subjects.