Impact of bronchodilator responsiveness classification changes on a large Australian community cohort

Abstract

RATIONALE Bronchodilator responsiveness (BDR) was redefined in the 2021 European Respiratory Society/American Thoracic Society (ERS-ATS) technical statement, from at least 200 mL absolute and 12% relative change in forced expiratory volume in 1 sec (FEV1) or forced vital capacity (FVC) in 2005 to more than 10% change from predicted values. OBJECTIVES The objectives of this research are to measure the impact of BDR reclassification and identify the characteristics of reclassified patients. METHODS A retrospective cohort analysis of a convenience sample of 2,065 tests. Repeat tests were excluded. MEASUREMENTS AND MAIN RESULTS A total of 1,429 tests were evaluated; 206 (14%) were BDR by one or both definitions; and 55/206 (27%) of these records were reclassified, with a close number of results newly classified as BDR (n = 27) and losing this classification (n = 28). Analyzing FEV1 only, 159 tests were BDR by one or both definitions; and 48/159 (30%) were reclassified, with 18 newly classified as BDR and 30 losing this classification. Analyzing FVC only, 101 tests were BDR by one or both definitions; and 27/101 (27%) were reclassified, with 19 newly classified as BDR and 8 losing this classification. Individuals with BDR that were reclassified were significantly heavier (81.8 vs 75.8 kg), and taller (170.6 vs 166.1 cm), although there was no significant difference in body mass index (BMI) (27.9 vs 27.3 kg/m2). They had smaller relative changes in FEV1 (12% vs 16%) and FVC (6% vs 12%), and greater baseline FEV1 (1.99 vs 1.74 L) and FVC (3.39 vs 2.97 L) and were more likely to be female (59% vs 42%). CONCLUSIONS More people were reclassified than expected. When evaluated by expiratory maneuver, there were less people classified as BDR using FEV1 in 2021 than 2005, and more using FVC. This analysis illustrates the potential clinical impact of the change in BDR definition.