Smith CJ, et al. - In this study including asthmatic children (44 poorly controlled/10 controlled), researchers compared the diagnostic accuracy of tests of large airways caliber (FEV₁, FEV₁/FVC, R20), peripheral zone properties [reactance (X5), ventilation heterogeneity (VH)], and airways inflammation (FeNO) as predictors of poor control. Following overnight bronchodilator withhold, a symptom-based control scale (ACT/cACT) and lung function tests were performed in 54 children enriched in severe asthma. Using area under the receiver operating characteristic (ROC) curve, sensitivity and specificity, they ranked the accuracy of each variable to predict poor control. With low sensitivity but perfect specificity, the highest ROC curve area was generated for the FEV₁% among measures of large airways caliber. With higher sensitivity but lower specificity compared to the FEV₁%, X5 and VH in the conducting zone had fair curve areas among measures of peripheral lung function. The accuracy of both, VH in the acinar zone and FeNO, was poor. Overall, as predictors of poor control, disparate performance of tests of large airway and peripheral zone lung function was seen.