Bronchial hyperresponsiveness (BHR) is an important, but not specific, asthma characteristic. We aimed to assess the predictive value of BHR tested by methacholine and exercise challenge at age 10 years for active asthma six years later.
METHODS: From a Norwegian birth cohort 530 children underwent methacholine challenge and exercise-induced bronchoconstriction (EIB) test (n= 478) at 10 years and structured interview and clinical examination at age 16 years. The methacholine dose causing 20% reduction in forced expiratory volume the first second (FEV1) (PD20) and the reduction in FEV1 (%) after a standardized treadmill test were used for BHR assessment. Active asthma was defined with at least two criteria positive: doctor's diagnosis of asthma, symptoms of asthma and/or treatment for asthma in the last year.
RESULTS: PD20 and EIB at 10 years of age increased the risk of asthma (β=0.94, (95% CI 0.92, 0.96) per μmol methacholine and β=1.10, (95% CI 1.06, 1.15) per per cent, respectively). Separately the tests explained 10 % and 7% respectively, and together 14% of the variation in active asthma six years later. The predicted probability for active asthma at the age of 16 years increased with decreasing PD20 and increasing EIB. The area under the curve (ROC curves) was larger for PD20 (0.69, 95% CI 0.62, 0.75) than for EIB (0.60, 95% CI 0.53, 0.67).
CONCLUSION: BHR at 10 years was a significant but modest predictor of active asthma six years later with methacholine challenge being superior to exercise test.
Authors: Riiser A, Hovland V, Carlsen KH, Mowinckel P, Lødrup Carlsen KC
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