A psychometric comparison of three patient-based measures of asthma control.

OBJECTIVE: Asthma is a multidimensional disease, characterized by changes in pulmonary function, transient and chronic symptoms, and effects on quality of life. In this study, we compared the psychometric properties and screening accuracy of three patient-based asthma control instruments including: the Asthma Control Test (ACT), a brief instrument developed to assess asthma control of patients in a clinical setting; the Asthma Control Questionnaire (ACQ), an instrument developed for use in clinical research; and the 'Rules of Two', a tool that has been used in both settings.

METHODS: Patients (N = 313) completed the ACT, ACQ, and Rules of Two during two asthma clinic visits 4-12 weeks apart. Office staff recorded pre- and post-bronchodilator FEV(1) measurements and asthma specialists provided a global rating of asthma control. Internal consistency reliability was computed and construct validity was evaluated using analysis of variance (ANOVA). Logistic regression and receiving operating characteristic (ROC) curve analysis was conducted to compare the screening accuracy of each measure in identifying patients with uncontrolled or moderate to severe asthma. The responsiveness of each measure to changes in asthma control and severity was tested using correlational and ANOVA methods.

RESULTS: Results show that the ACT and ACQ have comparable reliability, validity, screening accuracy, and responsiveness. The Rules of Two, however, did not meet some standards and therefore has weaker psychometric properties.

CONCLUSION: The ACT and ACQ are comparable asthma control questionnaires. The choice of which questionnaire to use should be informed by considering several factors, such as the intended purpose and setting where the questionnaire will be used, as well as the content, practicality, availability of benchmark scores, and adaptability to multiple administration modes of each questionnaire. One potential limitation of the study is that the data were collected in a clinical setting with limited demographic information. Hence, additional studies are needed to evaluate the psychometric properties of each instrument across demographic and clinical subgroups of the general population.