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A consistent response to bronchodilators over time associated with poor clinical outcomes in children, researchers find

Tuesday, December 16 2008 | Comments

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What's This? Researchers recently identified certain clinical parameters in children that are associated with a consistent response to inhaled beta-2 agonists, a phenotype they found to be linked with poor clinical outcomes.

The investigators explained that bronchodilator response (BDR) to inhaled beta-2 agonists among individuals with asthma is variable and that the significance of a consistent response over time is unknown. Therefore, they sought to determine which baseline clinical variables predict a consistent response to inhaled beta-2 agonists and which clinical outcomes might be associated with this phenotype. To do so, they analyzed data from 1,041 children with mild to moderate asthma participating in the Childhood Asthma Management Program (CAMP). The children were followed for an average of 4.3 years and underwent lung function studies and completed questionnaires at regular intervals during that time.

Consistent BDR was defined as a response of >=12% of the control value and a concomitant increase of 200 mL at each annual follow-up visit. The children who did not achieve either of these criteria were designated as nonresponders.

There were 52 children who had consistent BDRs during the 4-year trial. Several factors were identified that were baseline predictors of a consistent BDR, including lower baseline prebronchodilator forced expiratory volume in 1 second values (odds ratio [OR], 0.71; 95% CI, 0.63-0.81; P<.0001), higher log10 IgE levels (OR, 1.97; 95% CI, 1.18-3.30; P=.002), and lack of treatment with inhaled corticosteroids (OR, 0.31; 95% CI, 1.13-0.75; P=.009).

The researchers also found that children with a consistent BDR had significantly more hospital visits than children who were classified as nonresponders (relative rate [RR], 1.80; 95% CI, 1.20-2.80; P=.007). Children with a consistent BDR status also required more prednisone bursts (RR, 1.52; 95% CI, 1.20-1.95; P=.0007), had increased nocturnal awakenings caused by asthma (RR, 1.40; 95% CI, 1.20-1.65; P<.0001), and missed more days of school (RR, 1.43; 95% CI, 1.03-1.99; P=.03) relative to the nonresponders.

The researchers stated that a consistently positive response to inhaled bronchodilators should prompt physicians to reevaluate their patient's asthma medication regimens.

"Although this study sheds light on some of the clinical variables that contribute to the variability in response to inhaled bronchodilators, it is clear that other predictors not captured in our model are involved," the investigators added. "A better understanding of genetic predictors, environmental exposures, and gene-environment interactions is required to fully account for the heterogeneity in response to asthma medications." (Sharma S, et al. J Allergy Clin Immunol 2008;122:921-8.)

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