Evaluation of the National Heart, Lung, and Blood Institute guidelines impairment domain for classifying asthma control and predicting asthma exacerbations.

BACKGROUND: Accurate assessment of asthma control may help predict future asthma exacerbations.
OBJECTIVE: To evaluate asthma guidelines impairment domain components as predictors of exacerbations in severe/difficult-to-treat asthma.
METHODS: Children (aged 6-11 years; n = 289) and adolescents/adults (aged ≥ 12 years; n = 2,094) with complete baseline and 12-month data from The Epidemiology and Natural History of Asthma Outcomes and Treatment Regimens study were included. Asthma was categorized as very poorly controlled, not well-controlled, and well-controlled using impairment domain components. Effects of omitting each component on very poorly controlled and not well controlled groups were examined. Multivariable logistic regression determined the relationship of components in predicting asthma exacerbations.
RESULTS: Omission of individual impairment domain components led to misclassification of asthma control in 11% to 39% of patients. A baseline exacerbation was the strongest independent predictor of exacerbation at month 12 in children (odds ratio = 2.94; P < .001) and adolescents/adults (odds ratio = 2.93; P < .001). In children, very poorly controlled asthma-based short-acting β2-agonist use was associated with a 2-fold higher exacerbation risk (odds ratio = 2.03; P = .011). In adolescents/adults, not well controlled or very poorly controlled asthma based on short-acting β2-agonist use (odds ratio = 1.49), lung function (odds ratio = 1.66), and the Asthma Therapy Assessment Questionnaire (odds ratio = 1.94) were also independent predictors of exacerbations (P < .001).
CONCLUSIONS: Although the combined use of individual components of the impairment domain increases the sensitivity of identifying patients at high risk for future asthma exacerbations, specific components may be more important than others in severe/difficult-to-treat asthma. Prior exacerbations, short-acting β2-agonist use, lung function, and (in adolescents/adults) the Asthma Therapy Assessment Questionnaire were independent predictors of exacerbations.