Evaluation of clinically and physiologically atypical asthma: If it doesn't wheeze it may still be asthma

Objective: Children with asthma-like symptoms may not clinically wheeze. The objectives of this study were to evaluate if children, without physician-documented wheeze, wheeze during bronchial-challenge-testing (BCT), and if measurements of O₂Sat and respiratory rate during BCT improve the BCT sensitivity? Methods: Seven hundred and twenty-four children, who were referred for suspicion of asthma, performed a BCT. Positive BCT was determined by the provocation concentration (PC) which resulted in a 20% decrease in FEV₁ (PC₂₀), (in those who were able to perform spirometry, group B), or (in those unable to perform spirometry, group A) a 50% increase in respiratory rate (PC_RR), or a 5% decrease in oxygen-saturation (PC_O2-Sat) or appearance of wheezing (PC_wheeze). Results: Five hundred and seven BCTs were positive: group A n = 89 age, median (IQR), 3 (2.5–3.7) years (17.6%), were unable to perform spirometry, and group B n = 418 age 10.7 (6.8–15.6) years (82.4%), were able to perform spirometry. Children, without physician-documented wheeze in the total population (groups A plus B), were more likely (65.5%) to have a positive BCT without wheeze compared with those with physician-documented wheeze (41.0%, P < 0.001). In group A, adding PC_RR and PC_O2-Sat increased BCT sensitivity by 23.6%. Conclusions: Many children in both groups did not wheeze despite reaching BCT endpoints. Children without physician-documented wheeze tended not to wheeze at BCT. This may result in clinical under-diagnosis of asthma if depending on the presence of wheeze. In young children, adding PC_RR and PC_O2-Sat substantially increases BCT sensitivity and may improve asthma diagnosis.