Premium
Gender‐, age‐, and race/ethnicity‐based differential item functioning analysis of the movement disorder society–sponsored revision of the Unified Parkinson's disease rating scale
Author(s) -
Goetz Christopher G.,
Liu Yuanyuan,
Stebbins Glenn T.,
Wang Lu,
Tilley Barbara C.,
Teresi Jeanne A.,
Merkitch Douglas,
Luo Sheng
Publication year - 2016
Publication title -
movement disorders
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.352
H-Index - 198
eISSN - 1531-8257
pISSN - 0885-3185
DOI - 10.1002/mds.26847
Subject(s) - differential item functioning , psychology , rating scale , ethnic group , parkinsonism , statistic , item response theory , clinical psychology , disease , psychometrics , developmental psychology , medicine , statistics , pathology , mathematics , sociology , anthropology
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‐ R 2 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. © 2016 International Parkinson and Movement Disorder Society.