Severe Exacerbations in Children With Mild Asthma: Characterizing a Pediatric Phenotype

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Carroll CL, Schramm CM, Zucker AR. J Asthma. 2008;45(6):513–517PURPOSE OF THE STUDY. To describe a population of children with mild baseline asthma who were admitted to the ICU with severe exacerbations.STUDY POPULATION. A retrospective cohort study of 298 children with asthma (age: 2–18 years) who were admitted to the Connecticut Children's Medical Center ICU with a severe asthma exacerbation between April 1997 and December 2006 was performed.METHODS. Children were identified as having mild asthma if their disease was classified as intermittent or mild persistent according to current National Heart, Lung, and Blood Institute (NHLBI) guidelines; classifications of baseline asthma status were updated to current terminology for patients who were prospectively identified before the recent revisions to the NHLBI guidelines. The validated Modified Pulmonary Index Score was used to assess illness severity. Data regarding demographic characteristics, severity of illness at presentation, types and durations of therapies received, and duration of hospitalization were collected retrospectively.RESULTS. A total of 298 children with asthma were admitted to the ICU with severe exacerbations. Of those, 164 (55%) had previous mild intermittent or mild persistent asthma. These children, compared with children with moderate and severe persistent asthma, were noted to be younger (7.6 ± 3.9 vs 9.8 ± 4.6 years; P < .0001) and less likely to have been admitted to the hospital for asthma previously (42% vs 77%; P < .0001). In the mild asthma group, fewer Hispanic children (30% vs 47%; P = .003) and more white children (42% vs 24%; P = .001) were identified. Other demographic features were similar between the groups. No significant differences in the ICU length of stay, hospital length of stay, or therapies received existed between the 2 groups. Admission Modified Pulmonary Index Scores correlated closely with hospital length of stay. Thirteen children (8%) with mild asthma were intubated, which was fewer than those with moderate/severe persistent asthma (17%; P = .03). The intubated children with mild asthma were younger (6.9 ± 4.7 vs 11.4 ± 4.1 years; P = .009), less likely to be Hispanic, and less likely to have been previously intubated (P = .03).CONCLUSIONS. There was a significant subset of children with mild baseline asthma who developed severe exacerbations requiring ICU admission. These children were younger, were less likely to have a history of asthma-related admission, and had differences in race/ethnicity, compared with children with baseline moderate or severe asthmatic disease. These findings suggest that current classifications of pediatric asthma do not predict asthma phenotypes during acute exacerbations.REVIEWERS COMMENTS. This study reveals a trend toward younger white, rather than Hispanic or black, children diagnosed with mild asthma (according to current NHLBI classification criteria) requiring ICU admission. In addition, almost 10% of children with mild asthma classification required intubation during hospitalization. This raises concerns regarding the poor predictive capacity of the current classification system in identifying children at risk for severe exacerbations.