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Background: Preschool children with recurrent wheezing suffer high morbidity. It is unclear whether objective measures of asthma control, such as pulmonary function tests (PFTs), provide additional information to the clinical assessment., Methods: We recruited children between 3 and 6 years old, with a history of recurrent wheezing in the preceding year and treated for acute wheezing exacerbation in the emergency department (ED) into an observational cohort study. Children attended two outpatient visits: the first study visit within five days of discharge from the ED and the second study visit 12 weeks after the ED visit. We performed standardized symptom score (test for respiratory and asthma control in kids (TRACK)), multiple breath washout (MBW), spirometry, and clinical assessment at both visits., Results: Seventy-four children, mean (standard deviation (SD)) age of 4.32 years (0.84), attended both visits. Paired FEV 0.75 and lung clearance index (LCI) measurements at both time points were obtained in 37 and 34 subjects, respectively. Feasibility for all tests improved at visit 2 and was not age-dependent. At the second study visit, a third had controlled asthma based on the TRACK score, and the mean lung clearance index (LCI) improved from 9.86 to 8.31 (P = .003); however, 46% had an LCI in the abnormal range. FEV 0.75 z-score improved from -1.66 to -1.17 (P = .05) but remained in the abnormal range in 24%. LCI was abnormal in more than half of the children with "well-controlled" asthma based on the TRACK score. There was no correlation between PFT measures and TRACK scores at either visit., Conclusions: Lung clearance index demonstrates a persistent deficit post-exacerbation in a large proportion of preschoolers with recurrent wheezing, highlighting that symptom scores alone may not suffice for monitoring these children., (© 2020 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.)