Identifying Optimal Items in Quality of Life Assessment

摘要

Quality of life has drawn increasing attention in health science and more efforts have been devoted to develop instruments that are valid and reliable to assess quality of life. The World Health Organization (WHO) has devised an instrument World Health Organization Quality of Life Survey- Abbreviated Version (WHOQOL-BREF) to assess quality of life, but the psychometric property of each individual item has not been studied yet. Using item response theory, we examine the properties of the WHOQOL-BRIEF Taiwan version. Samejima’s graded response model was fitted, and item parameters were calculated. The items were ranked base on their discrimination power, and the best items are identified. Several data with subset of items (22, 20, 18, 16 and 14 items) were created by omitting items with lower discrimination power. The test information function of the full questionnaire and the subsets were compared. The results showed there were significant positive correlations between the full questionnaire and the subsets of items and the distributions are similar. The test information function showed the maximum amount of test information spaced over two ends of the theta continuum, and this suggested that the WHOQOL-BREF provided more information for groups with either lower or higher satisfaction of quality of life, while it is less discriminating for individuals in the middle range.