The Childhood Asthma Control Test: retrospective determination and clinical validation of a cut point to identify children with very poorly controlled asthma

Abstract

Background: The Childhood Asthma Control Test (C-ACT) has demonstrated validity in classifying children aged 4 to 11 years as having either "well-controlled" or "not well-controlled" asthma. However, new asthma management guidelines distinguish 3 levels of asthma control.

Objective: We sought to determine a second cut point on the C-ACT to identify children with "very poorly controlled" asthma.

Methods: Binomial logistic regression was performed on data from 671 children. The specialist's rating of control was the criterion measure. Specialists' severity ratings, specialists' assessment of therapy, and FEV(1) percent predicted were used to assess the clinical validity of the cut point.

Results: A cut point of 12 was selected because it correctly classified the highest percentage of participants (66.3%) as having "very poorly controlled" (vs "not well controlled") asthma and demonstrated high specificity (89.8%) and moderate positive predictive value (69.1%). Children scoring 12 or less versus 13 to 19 had lower mean FEV(1) percent predicted (79.8% vs 92.6%, P = .0002) and were more frequently stepped up in therapy (72.9% vs 53.6%, P = .0131) and rated as having severe asthma (13.6% vs 4.5%, P = .0005). One month later, significant differences in C-ACT scores and lung function between these 2 groups persisted. The mean C-ACT score of participants classified as "very poorly controlled" was significantly lower than that of participants classified as "not well-controlled" (17.2 vs 20.3, respectively; P = .0001).

Conclusion: A second cut point of 12 or less on the C-ACT identifies children with the lowest level of control, who are at risk for poorer outcomes, and is conceptually consistent with the classification of "very poorly controlled" asthma adopted by asthma management guidelines.