title: Lung function impairment evidenced by sequential specific airway resistance in childhood persistent asthma: a longitudinal study.
abstract: BACKGROUND
  Specific airway resistance (sRaw) is virtually independent of lung growth, height, and gender, thus facilitating longitudinal follow-up.
  
  
  OBJECTIVE
  To assess whether a specific phenotype of asthmatic children with a decline in lung function can be evidenced using sRaw.
  
  
  METHODS
  The authors hypothesized that sequential sRaw measurements over a long period would detect subtle trends. Clinical and functional data of children with persistent asthma under inhaled corticosteroids, evaluated at least three times per year for at least 4 years, were retrieved from a database.
  
  
  RESULTS
  One hundred fourteen children (30 girls) were followed for (median [interquartile range]) 6.9 years [5.6-7.9]. Data from 1699 measurements of sRaw (median 14/child) allowed the calculation of individual slopes of sRaw plotted against time demonstrating stable values in the group as a whole between 4 and 18 years. A positive correlation between individual slopes and the degree of intraindividual variation of sRaw was observed (R(2) = .16; p < .0001). Children with more than one positive skin test showed larger intrasubject variation of sRaw (p = .011). In 19/114 children (17%), a significant increase in sRaw of 12.3% per year (median) was observed. As compared to children without, those with a significant increase in sRaw were boys (p < .0001), had a lower initial (p = .008) and a higher final resistance (p = .025) but did not differ in terms of inhaled corticosteroid dose.
  
  
  CONCLUSIONS
  This retrospective study identifies a specific phenotype of asthmatic children that develops an impairment of lung function, confirming the results of a post hoc analysis of the Childhood Asthma Management Program study.
authors.affiliation: Cabinet La Berma, Antony, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Mahut
authors.forename: Ludovic
authors.initials: L
authors.lastname: Trinquart
authors.forename: Plamen
authors.initials: P
authors.lastname: Bokov
authors.forename: Claudine
authors.initials: C
authors.lastname: Peiffer
authors.forename: Christophe
authors.initials: C
authors.lastname: Delclaux
mesh_terms: D000293:Adolescent; D000403:Airway Resistance / Q000502:physiology*; D001249:Asthma / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008168:Lung / Q000503:physiopathology*; D008297:Male; D010993:Plethysmography, Whole Body; D012189:Retrospective Studies