This study aimed to assess the diagnostic utility of spirometry and impulse oscillometry, focusing on their correlation and diagnostic advantages, in children with cough variant asthma (CVA).

This study included children aged 5–12 years with a diagnosis of CVA who underwent sequential IOS and spirometry pulmonary function with bronchodilation (BD) tests. A control group of healthy children was matched. Receiver operating characteristic (ROC) curves were plotted, and the area under the curve (AUC) was calculated to assess the discriminatory potential of these spirometry and IOS parameters for CVA. The correlation and diagnostic consistency between spirometry and IOS parameters were compared.

A total of 177 patients with CVA and 45 control subjects were included. The ROC curve results for pre-BD parameters and the improvement rate showed that the combinations of “pre-MMEF(%pred) and _△MMEF” and “pre-Z5 (%pred) and -_△Z5 (%)” achieved the highest AUC value of 0.892 and 0.836, with threshold probabilities of 0.868, 0.786, respectively. The AUC values of these combined parameters surpassed those of individual ones. The correlation between spirometry and IOS parameters showed that pre-FEF₂₅ (%pred) has a moderately negative correlation with pre-Z5 (%pred) and pre-R5 (%pred) (r = −0.415, −0.404; P < 0.001), _△FEF₇₅ % has a weak positive correlation with -_△Z5 %, -_△R5 %(r = 0.154, 0.155; P < 0.05). The comparison of diagnostic consistency between pre-BD spirometry and pre-BD IOS parameters showed a weak correlation(kappa = 0.150, P = 0.007).

The changes in spirometry and IOS parameters during the BD test provided valuable diagnostic information for CVA and can help pediatricians accurately identify CVA in children.