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Methacholine, exercise challenge tests identified probable asthma in children

Methacholine and exercise challenge tests with impulse oscillometry were used to identify probable asthma in children with troublesome lung symptoms, according to recent study results.

Researchers studied 121 children (median age, 6 years; 61% boys), including 31 with probable asthma characterized by current troublesome lung symptoms, 61 with a history of early wheezing disorder, 15 with bronchopulmonary dysplasia (BPD) history and 14 healthy controls. Exercise and mannitol challenge tests were used to measure indirect airway hyperresponsiveness (AHR), with methacholine using impulse oscillometry (IOS) measuring direct AHR. A 40% or greater increase in respiratory resistance at 5 Hz defined AHR to exercise, with the dose to cause such an increase calculated in the mannitol and methacholine challenges.

All children participated in the exercise challenge, an outdoor running test for 6 to 8 minutes.  There were 27 positive test results, including 19 children (61%) in the troublesome lung symptoms cohort, six (10%) in the early wheezing cohort, two (13%) in the BPD group and zero in the control cohort.

“AHR to exercise was good at differentiating children with current troublesome lung symptoms from those in other groups (P<.001),” the researchers reported.

All children also participated in the methacholine test, with 84 positive results (69%), including 24 children (77%) in the troublesome lung symptoms cohort, 47 (77%) in the early wheezing cohort, 10 (67%) in the BPD group and three (21%) controls, with methacholine significantly distinguishing the troublesome lung symptoms cohort from the controls (P<.001).

Ninety-seven children performed the mannitol challenge test with positive results in three children (10%) in the troublesome lung symptoms cohort, four (7%) in the early wheezing cohort and three (20%) in the BPD cohort, with no significant difference among the groups.

“Methacholine and exercise challenges with IOS can be used to identify AHR in young children,” the researchers concluded. “Further studies are needed to understand the implication of AHR in young children and to assess reliable cutoff limits for pharmacologic agents in this age group.”

Disclosure: The researchers report no relevant financial disclosure.