Validity of the Asthma Control Test Questionnaire Among Smoking Asthmatics.

ABSTRACT

BACKGROUND: Smoking asthmatics respond worse to existing asthma therapies and have more asthma symptoms and exacerbations. OBJECTIVE: We evaluated the Asthma Control Test (ACT) for assessing asthma control among smokers. METHODS: Adults with asthma who smoked were enrolled and followed for 6 weeks. The statistical properties, validity, and responsiveness of the ACT were evaluated. Physician global assessment (GS) of asthma was the "gold standard." RESULTS: A total of 151 participants were enrolled 52% female and 48% male. The median (interquartile ranges) was 35 (27, 43) years for age, 11 (7, 18) for pack-years, and 16 (13, 20) for the ACT score. Participants self-identified as African American (49%), non-Hispanic whites (38%), and Hispanic whites (11%). Participants were classified as well controlled (24%), not well controlled (42%), or very poorly controlled (34%) at enrollment. Cronbach's alpha (95% confidence interval [CI]) for the ACT at enrollment was 0.81 (0.76, 0.85). The intraclass correlation coefficient (95% CI) for agreement of scores at enrollment and 6 weeks was 0.68 (0.57, 0.78) in participant with stable asthma (n = 93). ACT scores were associated with GS (P < .001). Area under the receiver operating characteristic (ROC) curve (95% CI) for an ACT cutoff score of ≤19 (not well controlled) was 0.76 (0.67, 0.84). The ACT score with the maximum area under the ROC curve was 18.6. CONCLUSIONS: The ACT questionnaire was reliable and discriminated between levels of asthma control in smoking asthmatics with similar sensitivity and specificity as nonsmoking asthmatics, which confirms its value as a tool for the management of asthma in this prevalent but understudied subgroup of subjects.