Combining small airway parameters with conventional parameters obtained during spirometry to diagnose airflow obstruction: A cross‐sectional study.

Background and Objective: The use of small airway parameters generated by spirometry, namely forced expiratory flow between 25% and 75% of forced vital capacity (FVC) (FEF25%–75%) and forced expiratory flow at 50% and 75% of FVC (FEF50% and FEF75%, respectively), is widely discussed. We evaluated the importance of these spirometric parameters in a large Chinese population. Methods: We conducted a cross‐sectional observational study in which spirometry and bronchodilator responsiveness (BDR) data were collected in a healthcare centre from May 2021 to August 2022 and in a tertiary hospital from January 2017 to March 2022. Discordance was assessed between the classification of test results by the large airway parameters of forced expiratory volume in 1 second (FEV1) and FEV1/FVC ratio and by the small airway parameters of FEF25%–75%, FEF75% and FEF50%. The predictive power of Z‐scores of spirometric parameters for airflow limitation and BDR was assessed using receiver operating characteristic curves. Results: Our study included 26,658 people. Among people with a normal FVC (n = 14,688), 3.7%, 4.5% and 3.6% of cases exhibited normal FEV1/FVC ratio but impaired FEF25%–75%, FEF75% and FEF50%, respectively, while 6.8%–7.0% of people exhibited normal FEV1 but impaired FEF25%–75%, FEF75% and FEF50%. Using the Z‐scores of combining both large and small airway parameters in spirometry showed the best area under the curve for predicting airflow limitation (0.90; 95% CI 0.87–0.94) and predicting BDR (0.72; 95% CI 0.71–0.73). Conclusion: It is important to consider both large and small airway parameters in spirometry to avoid missing a diagnosis of airflow obstruction. [ABSTRACT FROM AUTHOR]

Copyright of Respirology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)