A longitudinal study on the value of the methacholine challenge test as a diagnostic aid for asthma in high-risk adolescents
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Date
2012-11-23
Authors
Ong, Maggie
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Abstract
The objective of this study was to investigate the utility of the methacholine challenge test as a measure of airway hyperresponsiveness, in aiding the clinical diagnosis of asthma. The study comprised 330 high-risk 15-year-olds who have been followed since birth as a part of CAPPS, a multifaceted intervention trial on asthma prevention. Interventions consisting of HDM, pet, and ETS avoidance, maternal and infant dietary modifications, and daycare avoidance were implemented over the first year of life. Assessments at 15 years of age included a physician examination, methacholine challenge test, and skin prick test. ROC curves were constructed from sensitivities and specificities calculated for PC20 cut points from 1.0 to 8.0 mg/mL, using physician diagnosis as the gold standard. AUC's were calculated using the trapezoidal rule and the Delong method. An AUC of 0.73 was measured for asthma overall, which indicates that the methacholine challenge is a fair test (95% CI 0.65-0.82). This is an improvement from the value obtained at 7 years of age. When stratified by sex and atopy, and AUC of 0.50 was measured for adolescent females with non-atopic asthma, which describes it as a failure. The best PC20 cut point defining AHR in asthma overall was _< 5.5 mg/mL (sensitivity of 61.0% and specificity of 85.2%), which is an increase from the value at 7 years of age. These findings show that the methacholine challenge test is useful in assisting the diagnosis of asthma overall in high-risk adolescents, but not of non-atopic asthma in adolescent females.
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Medicine