January 29, 2015
WORCESTER, MA, January 29, 2015 — JWRG’s pursuit of disease-specific QOL measurement innovation appears to be on the right track toward filling the gap between disease-specific measures that do not measure QOL and QOL measures that are not disease-specific. Studies conducted during the development of the Quality of Life Disease Impact Scale (QDIS®) showed that it differs from widely-used disease-specific measures in a number of important ways. First, QDIS increases disease-specific QOL content representation enough to be on a par with widely-used generic QOL measures. At the same time, QDIS provides a single overall QOL impact score, despite its breadth of content. While QDIS item content overlaps substantially with the item content of generic measures, because QDIS items are disease-specific, QDIS consistently achieves greater convergent and discriminant validity in comparison with generic measures. QDIS also is the first disease-specific measure to be scored using norm-based scoring, based on a representative sample of the entire U.S. chronically ill general population, as opposed to a single disease. This advance in standardized scoring is based on evaluation of crucial assumptions about IRT item parameters used in scoring disease-specific QOL impact across diseases that were made during the development of QDIS. Due to its standardization of content and scoring across diseases, QDIS also is the first disease-specific measure that allows comparisons of disease-specific outcomes across diseases. Nina Deng and her UMass Medical School (UMMS) and JWRG collaborators tested assumptions underlying standardized scoring of QDIS, including differential item functioning (DIF) and other psychometric properties […]
