title: Bronchial Hyperresponsiveness to Methacholine and AMP in Children With Atopic Asthma.
abstract: OBJECTIVE
  Bronchial hyperresponsiveness (BHR) is typically measured by bronchial challenge tests that employ direct stimulation by methacholine or indirect stimulation by adenosine 5'-monophosphate (AMP). Some studies have shown that the AMP challenge test provides a better reflection of airway inflammation, but few studies have examined the relationship between the AMP and methacholine challenge tests in children with asthma. We investigated the relationship between AMP and methacholine testing in children and adolescents with atopic asthma.
  
  
  METHODS
  The medical records of 130 children with atopic asthma (mean age, 10.63 years) were reviewed retrospectively. Methacholine and AMP test results, spirometry, skin prick test results, and blood tests for inflammatory markers (total IgE, eosinophils [total count, percent of white blood cells]) were analyzed.
  
  
  RESULTS
  The concentration of AMP that induces a 20% decline in forced expiratory volume in 1 second [FEV1] (PC20) of methacholine correlated with the PC20 of AMP (r(2)=0.189, P<0.001). No significant differences were observed in the levels of inflammatory markers (total eosinophil count, eosinophil percentage, and total IgE) between groups that were positive and negative for BHR to methacholine. However, significant differences in inflammatory markers were observed in groups that were positive and negative for BHR to AMP (log total eosinophil count, P=0.023; log total IgE, P=0.020, eosinophil percentage, P<0.001). In contrast, body mass index (BMI) was significantly different in the methacholine positive and negative groups (P=0.027), but not in the AMP positive and negative groups (P=0.62). The PC20 of methacholine correlated with FEV1, FEV1/forced vital capacity (FVC), and maximum mid-expiratory flow (MMEF) (P=0.001, 0.011, 0.001, respectively), and the PC20 of AMP correlated with FEV1, FEV1/FVC, and MMEF (P=0.008, 0.046, 0.001, respectively).
  
  
  CONCLUSIONS
  Our results suggest that the AMP and methacholine challenge test results correlated well with respect to determining BHR. The BHR to AMP more likely implicated airway inflammation in children with atopic asthma. In contrast, the BHR to methacholine was related to BMI.
authors.affiliation: Department of Pediatrics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Childhood Asthma Atopy Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sung Han
authors.initials: SH
authors.lastname: Kang
authors.forename: Hyung Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Ju-Hee
authors.initials: JH
authors.lastname: Seo
authors.forename: Ji-Won
authors.initials: JW
authors.lastname: Kwon
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Jung
authors.forename: Young Hwa
authors.initials: YH
authors.lastname: Song
authors.forename: Soo-Jong
authors.initials: SJ
authors.lastname: Hong
keywords: AMP; atopic asthma; bronchial hyper-responsiveness; methacholine