Validity of the Asthma Control Test Questionnaire Among Smoking Asthmatics

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.