Validity, reliability and responsiveness of the "Schedule for the Evaluation of Individual Quality of Life – Direct Weighting" (SEIQoL-DW) in congenital heart disease

BACKGROUND: The 'Schedule for the Evaluation of Individual Quality of Life – Direct Weighting' (SEIQoL-DW) is an instrument developed to measure individual quality of life. Although this instrument has been used in numerous studies, data on validity and reliability are sparse. This study aimed to examine aspects of validity, reliability and responsiveness of the SEIQoL-DW on data obtained in adults with congenital heart disease, by using the new standards of psychological testing. METHODS: We evaluated validity evidence based on test content, internal structure, and relations to other variables, as well as the stability and responsiveness of the SEIQoL-DW. Evidence was provided by both theoretical considerations and empirical data. Empirical data were acquired from two studies. Firstly, using a cross-sectional study design, we included 629 patients with congenital heart disease. Secondly, 130 of the 629 initially included patients readministered the questionnaires approximately one year after the first data collection. In addition to the SEIQoL-DW, linear analog scales were used to assess overall quality of life and perceived health. RESULTS: We found that the SEIQoL-DW is not a valid measure of quality of life, but rather assesses determinants that contribute to individuals' quality of life. The SEIQoL-DW consistently proved to be valid and reliable to assess those determinants. However, responsiveness in patients with congenital heart disease may be problematic. CONCLUSION: Based on theoretical and empirical considerations, the SEIQoL-DW cannot be considered as a quality of life instrument. Nonetheless, it is a valid and reliable instrument to explore determinants for patients' quality of life.