Validation of the Spanish version of the Asthma Control Questionnaire.
BACKGROUND
The Asthma Control Questionnaire (ACQ) has not been validated in the Spanish population, and the fact that it requires spirometry poses an important limitation on its widespread use in the primary care setting in Spain.


OBJECTIVE
The aim of this study was to evaluate the psychometric properties of the Spanish version of the ACQ.


METHODS
In this multicenter, prospective study, consecutive adult patients with persistent asthma were recruited at 62 respiratory and allergy units across Spain. Patients were assessed at baseline and at weeks 2 and 6. The following clinical variables were recorded: lung function (forced expiratory volume in 1 second [FEV(1)]), symptoms, exacerbations, concomitant diseases, asthma severity according to the Global Initiative for Asthma international guideline, and asthma control as perceived by patients and physicians through direct ad hoc questions. The latter measures were derived specifically for this study. Patients self-completed the ACQ at all visits before the rest of the study variables were recorded. The ACQ's feasibility, validity, reliability, and sensitivity to change were assessed. Cross-sectional and longitudinal validity was assessed using the relationship between ACQ score and clinical parameters. Sensitivity to change was assessed by estimating the global effect size and the minimal important difference (MID). Reliability was assessed using estimation of the Cronbach alpha coefficient (CCalpha) and intraclass correlation coefficient (ICC).


RESULTS
A total of 607 patients were included. The mean (SD) age was 45.6 (17.1) years and 61.4% of the patients were women. Of these 607, 235 (39%) had mild asthma; 246 (41%), moderate; and 126 (21%), severe. Mean (SD) time to complete the ACQ was 3.9 (4.4) minutes. The Pearson correlation coefficient in the relationship between ACQ and FEV(1) (% predicted value) was -0.23. ACQ was found to be significantly related to asthma severity and intensity and frequency of symptoms (coughing, wheezing, and dyspnea) (both, P < 0.001). Change in ACQ was significantly related to changes in FEV(1), intensity and frequency of symptoms, and number of exacerbations (all, P < 0.001). The global effect size of ACQ was 0.46 and the MID was 0.47 point of a maximum of 6. CCalpha was 0.90 and ICC was 0.86.


CONCLUSION
In these adults with asthma in Spain, the Spanish version of the ACQ was found to be a reliable and valid questionnaire, suggesting that it can be used in this population as a discriminative and evaluative instrument.