Background
Bronchodilator responsiveness (BDR) is vital in diagnosing asthma and differentiating it from COPD, but its definition has been debated. The 2005 ATS/ERS guidelines define positive BDR as a 12% and 200 ml increase in FEV1 or FVC, but this has been criticized for favoring patients with lower lung function, older age, and taller height. In 2021, ATS/ERS proposed a new definition to address these biases, yet its clinical impact remains unclear. This study aims to assess the effect of adopting the 2021 BDR definition on patient classification and identify factors influencing reclassification.
Method
Anonymized pulmonary function test (PFT) data from patients of all ages between January 2014 and February 2022 were analyzed.
Three baseline spirometry tests, followed by administration of salbutamol, were conducted. Additional measurements, such as lung volumes, TLCO, and COPD Assessment Test (CAT), were performed if necessary. Patients were divided into four groups based on their bronchodilator responsiveness (BDR). 1) Positive BDR under both 2005 and 2021 definitions. 2) Negative BDR under both definitions 3) Negative under the 2005 definition but positive under the 2021 definition 4) Positive under the 2005 definition but negative under the 2021 definition.
Results
5653 patients were analyzed. Mean age was 57.2 years, and 51.6% were male. Obstructive spirometry was observed in 33% of subjects before bronchodilation, with signs of hyperinflation and reduced diffusion capacity. Overall, 12.4% met the 2005 BDR criterion, and 10.9% met the 2021 criterion. Reclassification occurred in 4.56% of patients, with more subjects transitioning from BDR positive (2005) to negative (2021) than vice versa. Younger patients were more likely to be reclassified as BDR positive under the new definition. Factors such as lower FEV1/FVC ratio, higher FENO, and alveolar volume were predictors of BDR reclassification from BDR negative to positive.
Conclusion
The adoption of the new BDR definition does not change the classification for the vast majority of individuals tested for clinical reasons. However, we found that adopting the new definition has a greater impact on adolescents and children than on adults. Children and adolescents are four times more likely to be reclassified from negative to positive than adults.