Lung function impairment evidenced by sequential specific airway resistance in childhood persistent asthma: a longitudinal study.
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.
Mahut
Bruno
B
Cabinet La Berma, Antony, France.
Trinquart
Ludovic
L
Bokov
Plamen
P
Peiffer
Claudine
C
Delclaux
Christophe
C
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