The 2021 ATS/ERS recommendations on interpreting lung function tests define a positive bronchodilator test response when there is increase of more than 10% in relation to the individual`s predicted value of FEV1 or FVC, differing from old 2005 ATS/ERS guidelines. A comparative study was carried out on the bronchodilator responsiveness test according to 2005 vs. 2021 ATS/ERS definition.

Materials and methods

Retrospective analysis of the bronchodilator response test, carried out consecutively from october 2018 until march 2020. Characterization of the result of the bronchodilator test, according 2005 and 2021 guidelines, were done.


A total of 1821 bronchodilation tests were analysed. It was found that 359 (19.7%) tests were positive according to 2005 ATS/ERS, compared to 305 (16.7%) according to 2021 ATS/ERS definition. Positivity was documented on 77 tests only according to 2005 ATS/ERS; only according to 2021 ATS/ERS on 23 tests; 282 in both criteria.

A total of 1439 tests were negative in both criteria. The coincidence rate (negative/negative or positive/positive) occurred in 94.5% of the sample.

It should be noted that on 5.5% of the tests the result changed from 2005 to 2021 criteria, from positive to negative result (4.2%; n=77) and from negative to positive (1.3%; n=24); a statistically significant change (p<0.001).

Concerning parameter where positivity was found, in the 2021 ATS/ERS criteria, positivity occurred only on FEV1 in 35.7%, only on FVC in 38.4%, and both FEV1 and FVC in 25.9%.


In this sample there was a significant decrease in the evidence of positive response to the bronchodilators according the new recommendation. Changes in clinical approach may occur.