Subjective symptomatology of asthma: validation of the asthma symptom checklist in an outpatient Spanish population.

The objective of this study was to validate the Asthma Symptom Checklist (ASC) so that it could be reliably used to assess the subjective symptomatology of asthma attacks in our context. Subjective symptomatology of asthma was examined in a group of 100 adult Spanish outpatients (57 women, 43 men; 17-69 years of age) with asthma. All of them completed the modified version of the ASC as well as questionnaires of depression, anxiety, and self-management of asthma (self-efficacy expectancies and health care utilization). Data about duration and severity of asthma, as well as dyspnea and %FEV1, were also recorded. The highest reliability Cronbach alpha indexes were for the panic-fear and fatigue scales. The oblique rotation of the ASC revealed five correlated factors (53% of the total variance explained): 1) panic-fear, 2) airways obstruction, 3) airways obstruction and panic-fear, 4) fatigue and irritability, 5) hyperventilation. The structure of factors was revalidated using orthogonal (varimax) rotation. Construct validity was examined by Person product-moment coefficient correlations, ANOVAs (asthma severity x ASC scores), and t-tests (sex by ASC scores). Panic-fear showed the best construct validity, as it was related to the severity of the asthma and the use of high-cost health care resources. There were no differences in ASC scores either on the basis of the asthma severity or on the sex of patients. The ASC factors represent stable components of subjective symptomatology of asthma attacks, especially with regard to the panic-fear and the hyperventilation subscales; however, the structure of the checklist as a whole was not identical to those reported in other studies. Correlations of the ASC with clinical variables related to asthma severity support the construct validity of the instrument and confirm its utility to evaluate the subjective symptomatology of asthma attacks in outpatients.