title: Useful parameters of bronchial hyperresponsiveness measured with an impulse oscillation technique in preschool children.
abstract: BACKGROUND
  There are few studies focused on bronchial challenge testing using the oscillation technique, and results from the test in preschool children have been inconsistent.
  
  
  OBJECTIVE
  The aim of this study was to explore which level of provocative concentration (PC) is appropriate for bronchial challenge testing using the impulse oscillometry system (IOS) for assessing asthma. The authors also compared variable diagnostic cutoff values of PC expressed in different ways.
  
  
  METHODS
  A methacholine challenge test was performed using an IOS and the mean baseline value, resistance (Rrs), reactance (Xrs), resonance frequency (Rf), and area of reactance (AX) of the respiratory system were recorded simultaneously over a frequency spectrum of 5 to 35 Hz in 50 preschool children with asthma and 41 children with chronic cough, serving as controls.
  
  
  RESULTS
  The results of the methacholine challenge test by IOS, expressed as percent changes of the predicted value (Delta%Pred), were significantly different between the two groups, whereas results expressed as actual data or Z-score were not. PC(80)_Xrs5 was a valuable diagnostic cutoff level for asthma with acceptable sensitivity (80.0%) and specificity (82.9%). The areas under the ROC curves of Xrs5 for both actual (0.867; p < .001) and predicted values (0.877; p < .001) were larger than those for Rrs5 (0.746 and 0.730, respectively).
  
  
  CONCLUSIONS
  The authors suggest PC(80)_Xrs5 might be a useful parameter for IOS-assessed bronchial challenge testing in preschool children with asthma.
authors.affiliation: Department of Pediatrics, CHA University School of Medicine, Seongnam, Korea.
authors.forename: Hye Mi
authors.initials: HM
authors.lastname: Jee
authors.forename: Ji Hee
authors.initials: JH
authors.lastname: Kwak
authors.forename: Da Woon
authors.initials: DW
authors.lastname: Jung
authors.forename: Man Yong
authors.initials: MY
authors.lastname: Han
mesh_terms: D016535:Bronchial Hyperreactivity / Q000175:diagnosis* / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D009991:Oscillometry; D012372:ROC Curve