title: Airway response to exercise measured by area under the expiratory flow-volume curve in children with asthma.
abstract: BACKGROUND
  The exercise challenge test is the gold standard for diagnosing exercise-induced bronchoconstriction; however, it produces negative results in many children with postexercise symptoms.
  
  
  OBJECTIVE
  To assess the utility of the area under the expiratory flow-volume curve (Aex) to identify exercise-induced bronchoconstriction in children with asthma.
  
  
  METHODS
  Data from the medical records of 221 children with asthma who underwent an exercise treadmill challenge (ETC) were analyzed. The relation between exercise-induced respiratory symptoms and results of the ETC were assessed, specifically, the maximal decrease in forced expiration in 1 second (FEV1) and the maximal decrease in the Aex.
  
  
  RESULTS
  The receiver operating characteristic curve showed that a decrease greater than 6% in the Aex was an optimal cutoff point to produce the fewest misclassified ETC results based on a greater than 10% decrease in FEV1. The results of multivariable logistic regression showed that a decrease greater than 6% in the Aex was comparable to a decrease greater than 10% in FEV1 during an ETC and was more closely related to the presence of exercise-induced respiratory symptoms. Measuring the Aex during a routine ETC allowed a confirmation of bronchoconstriction in an additional 49 children (44%) with asthma and exercise-induced respiratory symptoms. The Aex measurement increased the sensitivity and negative predictive value of ETC without a significant effect on ETC specificity.
  
  
  CONCLUSIONS
  Measuring the Aex increases the sensitivity and negative predictive value of ETC without producing a significant change in ETC specificity. Applying a 6% decrease in the Aex as a cutoff point for a positive exercise challenge test result may prevent the underdiagnosis of exercise-induced bronchoconstriction in children with asthma and postexercise symptoms.
  
  
  BACKGROUND
  This study was registered at www.clinicaltrials.gov (NCT01798823).
authors.affiliation: Department of Pediatrics and Allergy, Medical University of Lodz, N Copernicus Hospital, Lodz, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Majak
authors.forename: Lukasz
authors.initials: L
authors.lastname: Cichalewski
authors.forename: Agata
authors.initials: A
authors.lastname: Ożarek-Hanc
authors.forename: Włodzimierz
authors.initials: W
authors.lastname: Stelmach
authors.forename: Joanna
authors.initials: J
authors.lastname: Jerzyńska
authors.forename: Iwona
authors.initials: I
authors.lastname: Stelmach
mesh_terms: D000293:Adolescent; D001250:Asthma, Exercise-Induced / Q000175:diagnosis* / Q000503:physiopathology*; D016084:Bronchoconstriction; D002648:Child; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male