Development and evaluation of an asthma-Specific quality of life (A-QOL) questionnaire

Background. Few health-related quality of life (HRQOL) studies of asthma patients have been conducted in Korea, mainly due to the lack of a psychometrically validated asthma-specific instrument. Objective. The aims of the present study were to develop and evaluate an instrument for assessing HRQOL in Korean asthma patients (asthma-specific quality of life, [A-QOL]). Methods. Items were generated using in-depth interviews and a review of the literature and were subsequently reviewed by a panel of experts. Content-validated items were evaluated psychometrically with the aid of 422 asthma patients who were recruited from university hospitals in South Korea. The participants were asked to complete a preliminary A-QOL questionnaire (comprising the content-validated items), the Asthma Control Test, the Center for Epidemiologic Studies-Depression Survey (CES-D), and the Short Form-36 Health Survey. The Global Initiative for Asthma Guideline classification was also used to classify the severity of asthma. The psychometric properties of the data were analyzed. Results: Thirty-six preliminary items were generated, from which factor analysis extracted a six-factor solution. Six of the items were not loaded significantly on any of the factors, such that they were not heterogeneous items. Multi-trait scaling analysis supported item convergence and discriminant validity. The A-QOL was associated significantly with the CES-D. Patients with controlled asthma had higher A-QOL scores than those whose asthma was not controlled. The quality of life measured by the A-QOL was more sensitive than that measured by the generic Short Form-36 Health Survey. The values of Cronbach's alpha for the subscales of the A-QOL were all greater than 0.70. The responsiveness of all subscales, excluding the environmental distress subscale, was established. Conclusions. The A-QOL is an easily applied tool that exhibits good psychometric properties for asthma patients. The A-QOL questionnaire is valid for and can be used reliably in both practice and clinical trials.