Differential item functioning in the Unified Dyskinesia Rating Scale (UDysRS)

Abstract

Objective Test if differential item functioning due to gender, age, race/ethnicity or education impacts Unified Dyskinesia Rating Scale scores. Background Testing rating scales for differential item functioning is a core validation step. If differential item functioning exists, interpretation of item scores must consider secondary influences on dyskinesia ratings. Methods Using Unified Dyskinesia Rating Scale translation databases (N=3,132), we tested uniform and non-uniform differential item functioning. We required confirmation by two independent methods and considered differential item functioning pertinent if McFadden pseudo R2 magnitude statistics exceeded negligible ratings. Results No age, race/ethnicity or education non-uniform differential item functioning was identified. Gender non-uniform differential item functioning occurred for two items, both with negligible magnitude. Gender, race, and education uniform differential item functioning was observed for multiple items, all with negligible magnitude. Conclusions The Unified Dyskinesia Rating Scale items effectively capture dyskinesia severity without pertinent gender, age, race/ ethnicity or education influence.

Minimal clinically important difference for the historic parts of the Unified Dyskinesia Rating Scale

“…Recently a single, comprehensive rating scale, called the Unified Dyskinesia Rating Scale (UDysRS), was developed to assess the most important dimensions of motor complications [1]. The development of the scale was mainly clinimetrically driven [2] to simultaneously and reliably measure various aspects of the motor complications [3]. The UDysRS consists of four different subscales representing different domains:…”

Bridging the gap between statistical significance and clinical relevance: A systematic review of minimum clinically important difference (MCID) thresholds of scales reported in movement disorders research

“…UDysRS has been found to be clinimetrically sound for dyskinesia in Parkinson's disease, demonstrating acceptable levels of internal consistency, inter- and intra-rater reliability, and construct validity [ 55 , 56 ]. It has also been demonstrated to be highly stable for individual patient's ON and OFF periods, making it a reliable estimate of scores [ 51 ].…”

Assessing tilavonemab efficacy in early Alzheimer's disease via longitudinal item response theory modeling

“…Moreover, differential item functioning (DIF) arises in the CDR when item response probabilities of a domain vary among individuals with similar latent AD severity but differ by a covariate such as treatment group. While testing for DIF is crucial in scale validation, typically performed using cross‐sectional IRT models as demonstrated in our previous studies, 34 , 35 current methodologies do not readily apply to the longitudinal IRT framework utilized in this research. This gap underscores the need for further methodological development to accurately assess DIF in longitudinal contexts.…”