Christopher G Goetz1, Yuanyuan Liu2, Glenn T Stebbins1, Lu Wang2, Barbara C Tilley2, Jeanne A Teresi3,4, Douglas Merkitch1, Sheng Luo2. 1. Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois, USA. 2. Department of Biostatistics, University of Texas Health Science Center, School of Public Health, Houston, Texas, USA. 3. Columbia University Stroud Center at New York State Psychiatric Institute, New York, NY, USA. 4. Research Division, Hebrew Home at Riverdale, RiverSpring Health, New York, NY, USA.
Abstract
OBJECTIVE: Assess MDS-UPDRS items for gender-, age-, and race/ethnicity-based differential item functioning. BACKGROUND: Assessing differential item functioning is a core rating scale validation step. For the MDS-UPDRS, differential item functioning occurs if item-score probability among people with similar levels of parkinsonism differ according to selected covariates (gender, age, race/ethnicity). If the magnitude of differential item functioning is clinically relevant, item-score interpretation must consider influences by these covariates. Differential item functioning can be nonuniform (covariate variably influences an item-score across different levels of parkinsonism) or uniform (covariate influences an item-score consistently over all levels of parkinsonism). METHODS: Using the MDS-UPDRS translation database of more than 5,000 PD patients from 14 languages, we tested gender-, age-, and race/ethnicity-based differential item functioning. To designate an item as having clinically relevant differential item functioning, we required statistical confirmation by 2 independent methods, along with a McFadden pseudo-R2 magnitude statistic greater than "negligible." RESULTS: Most items showed no gender-, age- or race/ethnicity-based differential item functioning. When differential item functioning was identified, the magnitude statistic was always in the "negligible" range, and the scale-level impact was minimal. CONCLUSIONS: The absence of clinically relevant differential item functioning across all items and all parts of the MDS-UPDRS is strong evidence that the scale can be used confidently. As studies of Parkinson's disease increasingly involve multinational efforts and the MDS-UPDRS has several validated non-English translations, the findings support the scale's broad applicability in populations with varying gender, age, and race/ethnicity distributions.
OBJECTIVE: Assess MDS-UPDRS items for gender-, age-, and race/ethnicity-based differential item functioning. BACKGROUND: Assessing differential item functioning is a core rating scale validation step. For the MDS-UPDRS, differential item functioning occurs if item-score probability among people with similar levels of parkinsonism differ according to selected covariates (gender, age, race/ethnicity). If the magnitude of differential item functioning is clinically relevant, item-score interpretation must consider influences by these covariates. Differential item functioning can be nonuniform (covariate variably influences an item-score across different levels of parkinsonism) or uniform (covariate influences an item-score consistently over all levels of parkinsonism). METHODS: Using the MDS-UPDRS translation database of more than 5,000 PDpatients from 14 languages, we tested gender-, age-, and race/ethnicity-based differential item functioning. To designate an item as having clinically relevant differential item functioning, we required statistical confirmation by 2 independent methods, along with a McFadden pseudo-R2 magnitude statistic greater than "negligible." RESULTS: Most items showed no gender-, age- or race/ethnicity-based differential item functioning. When differential item functioning was identified, the magnitude statistic was always in the "negligible" range, and the scale-level impact was minimal. CONCLUSIONS: The absence of clinically relevant differential item functioning across all items and all parts of the MDS-UPDRS is strong evidence that the scale can be used confidently. As studies of Parkinson's disease increasingly involve multinational efforts and the MDS-UPDRS has several validated non-English translations, the findings support the scale's broad applicability in populations with varying gender, age, and race/ethnicity distributions.
Authors: Maria Orlando Orlando Edelen; David Thissen; Jeanne A Teresi; Marjorie Kleinman; Katja Ocepek-Welikson Journal: Med Care Date: 2006-11 Impact factor: 2.983
Authors: Christopher G Goetz; Barbara C Tilley; Stephanie R Shaftman; Glenn T Stebbins; Stanley Fahn; Pablo Martinez-Martin; Werner Poewe; Cristina Sampaio; Matthew B Stern; Richard Dodel; Bruno Dubois; Robert Holloway; Joseph Jankovic; Jaime Kulisevsky; Anthony E Lang; Andrew Lees; Sue Leurgans; Peter A LeWitt; David Nyenhuis; C Warren Olanow; Olivier Rascol; Anette Schrag; Jeanne A Teresi; Jacobus J van Hilten; Nancy LaPelle Journal: Mov Disord Date: 2008-11-15 Impact factor: 10.338