Distinguishing characteristics of difficult-to-control asthma in inner-city children and adolescents.
BACKGROUND
Treatment levels required to control asthma vary greatly across a population with asthma. The factors that contribute to variability in treatment requirements of inner-city children have not been fully elucidated.


OBJECTIVE
We sought to identify the clinical characteristics that distinguish difficult-to-control asthma from easy-to-control asthma.


METHODS
Asthmatic children aged 6 to 17 years underwent baseline assessment and bimonthly guideline-based management visits over 1 year. Difficult-to-control and easy-to-control asthma were defined as daily therapy with 500 μg of fluticasone or greater with or without a long-acting β-agonist versus 100 μg or less assigned on at least 4 visits. Forty-four baseline variables were used to compare the 2 groups by using univariate analyses and to identify the most relevant features of difficult-to-control asthma by using a variable selection algorithm. Nonlinear seasonal variation in longitudinal measures (symptoms, pulmonary physiology, and exacerbations) was examined by using generalized additive mixed-effects models.


RESULTS
Among 619 recruited participants, 40.9% had difficult-to-control asthma, 37.5% had easy-to-control asthma, and 21.6% fell into neither group. At baseline, FEV1 bronchodilator responsiveness was the most important characteristic distinguishing difficult-to-control asthma from easy-to-control asthma. Markers of rhinitis severity and atopy were among the other major discriminating features. Over time, difficult-to-control asthma was characterized by high exacerbation rates, particularly in spring and fall; greater daytime and nighttime symptoms, especially in fall and winter; and compromised pulmonary physiology despite ongoing high-dose controller therapy.


CONCLUSIONS
Despite good adherence, difficult-to-control asthma showed little improvement in symptoms, exacerbations, or pulmonary physiology over the year. In addition to pulmonary physiology measures, rhinitis severity and atopy were associated with high-dose asthma controller therapy requirement.
['Pongracic|Jacqueline A|JA|', 'Krouse|Rebecca Z|RZ|', 'Babineau|Denise C|DC|', 'Zoratti|Edward M|EM|', 'Cohen|Robyn T|RT|', 'Wood|Robert A|RA|', 'Khurana Hershey|Gurjit K|GK|', 'Kercsmar|Carolyn M|CM|', 'Gruchalla|Rebecca S|RS|', 'Kattan|Meyer|M|', 'Teach|Stephen J|SJ|', 'Johnson|Christine C|CC|', 'Bacharier|Leonard B|LB|', 'Gern|James E|JE|', 'Sigelman|Steven M|SM|', 'Gergen|Peter J|PJ|', 'Togias|Alkis|A|', 'Visness|Cynthia M|CM|', 'Busse|William W|WW|', 'Liu|Andrew H|AH|']
D000293:Adolescent D017668:Age of Onset D018927:Anti-Asthmatic Agents D001249:Asthma D015142:Baltimore D002648:Child D005260:Female D006801:Humans D008137:Longitudinal Studies D008297:Male D008487:Medical History Taking D011203:Poverty D011446:Prospective Studies D012220:Rhinitis D012720:Severity of Illness Index D014505:Urban Population
asthma rhinitis Child IgE allergen sensitization asthma exacerbations asthma morbidity asthma phenotype asthma severity inner-city asthma pulmonary function