Spirometry estimation of central airway dysanapsis on computed tomography in healthy subjects without active lung diseases.

The original concept of the airway-to-lung size mismatch, termed dysanapsis, was introduced on spirometry and was extended by computed tomography (CT) evaluation of the central airways. CT-assessed dysanapsis allows a risk estimation of lung disease development in healthy subjects, although radiation exposure limits its use, particularly for younger subjects. This study investigated which spirometry indices can be used to estimate CT-assessed central airway dysanapsis in healthy subjects. In consecutive lung cancer screening subjects without active lung diseases, the dysanapsis ratio (DR), forced mid-expiratory flow/forced vital capacity (FEF_25-75/FVC), forced expiratory volume in 1 s/FVC (FEV₁/FVC), and peak expiratory flow/FVC (PEF/FVC) were obtained via spirometry. The airway-to-lung size ratio for four locations, including the trachea, both main bronchi, and bronchus intermedius (ALR4), and for 14 locations, including the same four airways and 10 segmental and subsegmental airways (ALR14), were obtained via CT. According to the quartiles of the ALR14 or ALR4, 163 male and 190 female subjects were divided into four groups. CT-assessed dysanapsis was defined as the lowest quartile of the ALR14 (or ALR4). Among the spirometry indices, the area under the curve (AUC) for detecting the lowest ALR14 group was the highest for DR (0.80 and 0.78 for males and females, respectively). In contrast, the AUC for detecting the lowest ALR4 group was the highest for PEF/FVC (0.67 and 0.77 for males and females, respectively). DR and PEF/FVC on spirometry could be associated with CT-assessed dysanapsis, but the associations varied depending on the airway locations used for the ALR calculation.NEW & NOTEWORTHY The airway-to-lung size discrepancy on computed tomography (CT-assessed dysanapsis) highlights a lifelong risk for developing lung diseases. This study demonstrated that the spirometric index of the dysanapsis ratio can be used for estimating CT-assessed dysanapsis of the entire central airway tree from the trachea to subsegmental airways, whereas a novel index, peak expiratory flow/forced vital capacity (PEF/FVC), can be used for estimating CT-assessed dysanapsis of the extrapulmonary airways (the trachea, main bronchus, and bronchus intermedius).