Item Response Theory Analysis of the MDS-UPDRS Motor Examination: Tremor vs. Nontremor Items.

Tosin, Michelle Hyczy de Siqueira

Goetz, Christopher G

Luo, Sheng

Choi, Dongrak

Stebbins, Glenn T

2020-07-01T13:53:12Z

2020-07-01T13:53:12Z

2020-05-29

2020-07-01T13:53:08Z

BACKGROUND:In PD, tremor severity behaves differently from other core motor features. However, the most commonly used assessment of overall motor severity, total MDS-UPDRS Motor Examination (Part 3) score, does not account for this distinction. OBJECTIVES:To investigate the Motor Examination (Part 3) using Item Response Theory approaches focusing on sample-independent strategies that assess how well items measure latent models of PD motor severity. METHODS:Data from 6,298 PD patients were analyzed with graded response model Item Response Theory approaches involving two analyses all 33 Part 3 items versus the 10 tremor items and 23 bradykinesia, rigidity, gait, and posture items considered separately. The strength of relationship between items and the latent measure of parkinsonian motor severity (discrimination parameter) and calculated thresholds (location parameters) were assessed using the mirt program implemented in R (R Foundation for Statistical Computing, Vienna, Austria). RESULTS:Analyzing all Part 3 items together, nontremor items demonstrated good discrimination parameters (mean = 1.83 ± 0.37) and range of thresholds (-1.73 to +4.42), but tremor items had poor discrimination (mean = 0.52 ± 0.76) and thresholds (-0.69 to 14.29). Segregating nontremor from tremor items in two independent analyses provided markedly improved discrimination and location parameters for both. CONCLUSIONS:MDS-UPDRS Part 3 tremor and nontremor items have very different relations to the construct of PD severity. Strongly improved clinimetric properties for Part 3 are obtained when tremor and nontremor items are considered separately. We suggest that evaluating PD motor severity, as an operationalized summary measure, is best attained through separate analyses with tremor and nontremor motor scores. © 2020 International Parkinson and Movement Disorder Society.

0885-3185

1531-8257

https://hdl.handle.net/10161/21104

eng

Wiley

Movement disorders : official journal of the Movement Disorder Society

10.1002/mds.28110

MDS-UPDRS

Parkinson's disease

clinimetrics

item response theory

Item Response Theory Analysis of the MDS-UPDRS Motor Examination: Tremor vs. Nontremor Items.

Journal article

Luo, Sheng|0000-0003-4214-5809

School of Medicine

Duke Clinical Research Institute

Biostatistics & Bioinformatics

Duke

Institutes and Centers

Basic Science Departments

Published