Development and Validation of the Cystic Fibrosis Questionnaire in the United States: A Health-Related Quality-of-Life Measure for Cystic Fibrosis

Abstract

The Cystic Fibrosis Questionnaire (CFQ) is a disease-specific instrument that measures health-related quality of life (HRQOL) for adolescents and adults with cystic fibrosis (CF) > or = 14 years, consisting of 44 items on 12 generic and disease-specific scales. Versions of the CFQ are also available for children with CF and their parents. This study evaluated the psychometric properties of the CFQ in a national study at 18 CF centers in the United States. The CFQ-teen/adult was administered to 212 patients with CF ranging in age from 14 to 53 years. Test-retest reliability was assessed in a subset of patients over a 10- to 14-day interval. Multitrait analysis indicated a majority of items (95%) correlated more highly with their intended scale than a competing scale, supporting the conceptual model. Internal consistency coefficients indicated the CFQ scales had good reliability (Cronbach alpha = 0.67 to 0.94), and test-retest stability was acceptable (rs = 0.45 to 0.90). Validity was demonstrated by examining relationships between the CFQ, age, pulmonary function, and body mass index. As expected, the CFQ was inversely correlated with age, with older adults reporting lower CFQ scores than younger adults, better nutritional status was positively correlated with several weight-related scales, and the measure differentiated between individuals with varying levels of disease severity. Strong associations were also found between the CFQ and similar scales on the Short Form-36 Health Questionnaire, a well-known generic HRQOL measure. The results demonstrated that the CFQ-teen/adult is a reliable and valid measure of HRQOL for individuals with CF. It may be utilized in clinical trials to assess the effects of new therapies, to document the progression of disease, and to inform clinical practice.