title: Relationships of methacholine and AMP responsiveness with peak expiratory flow variability in children with asthma.
abstract: BACKGROUND
  Both bronchial responsiveness (BR) and peak expiratory flow (PEF) variability are increased in asthma. PEF variability is presumed to reflect the degree of BR in asthma. BR is commonly assessed by bronchial challenges using direct or indirect stimuli.
  
  
  OBJECTIVE
  The aim of this study was to compare methacholine and adenosine 5'-monophosphate (AMP) responsiveness with regard to their relationships with PEF variability in children with asthma.
  
  
  METHODS
  Methacholine and AMP challenge tests were performed in 79 children with mild to moderate asthma, and a provocative concentration causing a 20% decline in forced expiratory volume in 1 s (PC(20)) was calculated for each challenge. Subjects recorded PEF each morning and each evening for 14 consecutive days. PEF variability was expressed as amplitude percentage mean (amp%mean; high PEF minus low PEF on each day, expressed as a percentage of their mean, averaged over 14 days), and as the lowest percentage highest (low%high; the lowest PEF expressed as a percentage of the highest PEF recorded over the period).
  
  
  RESULTS
  Methacholine PC(20) correlated significantly but weakly with both indices of PEF variability (amp%mean: r=-0.285, P=0.011; low%high: r=0.238, P=0.034). However, there was a significant and strong correlation between AMP PC(20) and both amp%mean (r=-0.583, P=0.000) and low%high (r=0.496, P=0.000). For AMP PC(20), the correlations were stronger than for methacholine PC(20) (comparison of correlation coefficients with amp%mean: P=0.021; with low%high: P=0.063).
  
  
  CONCLUSIONS
  Both methacholine PC(20) and AMP PC(20) correlated significantly with PEF variability. However, the stronger correlations for AMP PC(20) than for methacholine PC(20) suggest that PEF variability may be better reflected by BR assessed by AMP than by methacholine.
authors.affiliation: Department of Pediatrics, Korea University Anam Hospital, Seoul, Korea.
authors.forename: Y
authors.initials: Y
authors.lastname: Yoo
authors.forename: D K
authors.initials: DK
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Yu
authors.forename: S H
authors.initials: SH
authors.lastname: Choi
authors.forename: C K
authors.initials: CK
authors.lastname: Kim
authors.forename: Y Y
authors.initials: YY
authors.lastname: Koh
mesh_terms: D000249:Adenosine Monophosphate / Q000008:administration & dosage*; D000293:Adolescent; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage*; D018721:Muscarinic Agonists / Q000008:administration & dosage*; D010366:Peak Expiratory Flow Rate / Q000187:drug effects*; D015203:Reproducibility of Results
chemical_list: D018721:Muscarinic Agonists; D016210:Methacholine Chloride; D000249:Adenosine Monophosphate