• Bruno Mahut, Ludovic Trinquart, Plamen Bokov, Claudine Peiffer, and Christophe Delclaux.
• Cabinet La Berma, Antony, France.
• J Asthma. 2010 Aug 1;47(6):655-9.

BackgroundSpecific airway resistance (sRaw) is virtually independent of lung growth, height, and gender, thus facilitating longitudinal follow-up.ObjectiveTo assess whether a specific phenotype of asthmatic children with a decline in lung function can be evidenced using sRaw.MethodsThe 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.ResultsOne 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.ConclusionThis 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.

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