To address the question: How well does bronchial hyperresponsiveness (BHR) predict later clinical asthma?
Five hundred thirty children in a prospective population-based birth cohort underwent a methacholine challenge and exercise challenge on separate days at age 10 years. At age 16 years, they underwent a clinical evaluation and repeat methacholine challenge.
BHR was scored as follows based the methacholine dose causing a 20% drop in FEV1 (PD20): severe ≤1 µmol, mild to moderate 1 to 8, and borderline 8 to 16. Exercise-induced bronchospasm (EIB) is defined as ≥10% reduction in forced expiratory volume in 1 second 3 to 20 minutes after running. Active asthma is defined as at least 2 of the following: doctor’s diagnosis of asthma, asthma symptoms during the last 12 months, and use of asthma medication during the last 12 months.
Active asthma at age 16 was observed in 74% of the children with active asthma, and...