Browsing by Author "Choi, Dongrak"
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Item Open Access AN INTEGRATIVE MODELING FRAMEWORK FOR MULTIVARIATE LONGITUDINAL CLINICAL DATA(2024) Choi, DongrakThis dissertation is centered on the development of innovative statistical methodologies specifically tailored to address the complex nature of multivariate data associated with Parkinson's disease (PD). PD is known to manifest impairments across both behavioral and cognitive domains, and as of now, there are no available disease-modifying treatments. Consequently, researchers typically gather a diverse array of data types, encompassing binary, continuous, categorical outcomes, and time-to-event data, in order to gain a comprehensive understanding of the multifaceted aspects of this disorder. Furthermore, due to the long follow-up of PD studies, the occurrence of intermittent missing data is a common challenge, which can introduce bias into the analysis. In this dissertation, we introduce novel approaches for jointly modeling multivariate longitudinal outcomes and time-to-event data using functional latent trait models and generalized multivariate functional mixed models to deal with different types of data. Additionally, we present a method for the detection and handling of missing data patterns through the utilization of joint modeling techniques.
Item Open Access Expanded and Independent Spanish validation of the MDS ‐ Non Motor Rating Scale(Movement Disorders Clinical Practice) Cubo, Esther; Luo, Sheng; Martínez-Martín, Pablo; Stebbins, Glenn T; Lin, Jeffrey; Choi, Dongrak; García-Bustillo, Alvaro; Mir, Pablo; Santos-Garcia, Diego; Serrano-Dueñas, Marcos; Rodriguez-Violante, Mayela; Singer, Carlos; and the Spanish MDS‐NMS Validation Study GroupItem Open Access It Is as It Was: MDS-UPDRS Part III Scores Cannot Be Combined with Other Parts to Give a Valid Sum.(Movement disorders : official journal of the Movement Disorder Society, 2022-12) Goetz, Christopher G; Choi, Dongrak; Guo, Yuanyuan; Stebbins, Glenn T; Mestre, Tiago A; Luo, ShengBackground
Original clinimetric analyses by the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) developers did not confirm the validity of summing the scores of its parts. Recent studies used the summed score of Part III and other parts as efficacy outcomes.Objective
The aim of this study was to establish whether summing scores of MDS-UPDRS parts can be recommended.Methods
Using 7466 full MDS-UPDRS scores, we applied two-step factor analysis as in the original article to reassess the validity analysis with the threshold criterion set at comparative fit index ≥0.9.Results
All comparative fit indexes of any combination including Part III were lower than 0.90.Conclusions
Summing Part III MDS-UPDRS scores with other parts is not clinimetrically sound. The MDS-UPDRS is a validated four-part scale with corresponding individual part scores and needs to be used within the limits originally presented. © 2022 International Parkinson and Movement Disorder Society.Item Open Access Item Response Theory Analysis of the MDS-UPDRS Motor Examination: Tremor vs. Nontremor Items.(Movement disorders : official journal of the Movement Disorder Society, 2020-05-29) Tosin, Michelle Hyczy de Siqueira; Goetz, Christopher G; Luo, Sheng; Choi, Dongrak; Stebbins, Glenn TBACKGROUND: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.Item Open Access Novel Approach to Movement Disorder Society–Unified Parkinson's Disease Rating Scale Monitoring in Clinical Trials: Longitudinal Item Response Theory Models(Movement Disorders Clinical Practice, 2021-01-01) Luo, Sheng; Zou, Haotian; Goetz, Christopher G; Choi, Dongrak; Oakes, David; Simuni, Tanya; Stebbins, Glenn TBackground: Although nontremor and tremor Part 3 Movement Disorder Society–Unified Parkinson's Disease Rating Scale items measure different impairment domains, their distinct progression and drug responsivity remain unstudied longitudinally. The total score may obscure important time-based and treatment-based changes occurring in the individual domains. Objective: Using the unique advantages of item response theory (IRT), we developed novel longitudinal unidimensional and multidimensional models to investigate nontremor and tremor changes occurring in an interventional Parkinson's disease (PD) study. Method: With unidimensional longitudinal IRT, we assessed the 33 Part 3 item data (22 nontremor and 10 tremor items) of 336 patients with early PD from the STEADY-PD III (Safety, Tolerability, and Efficacy Assessment of Isradipine for PD, placebo vs. isradipine) study. With multidimensional longitudinal IRT, we assessed the progression rates over time and treatment (in overall motor severity, nontremor, and tremor domains) using Markov Chain Monte Carlo implemented in Stan. Results: Regardless of treatment, patients showed significant but different time-based deterioration rates for total motor, nontremor, and tremor scores. Isradipine was associated with additional significant deterioration over placebo in total score and nontremor scores, but not in tremor score. Further highlighting the 2 separate latent domains, nontremor and tremor severity changes were positively but weakly correlated (correlation coefficient, 0.108). Conclusions: Longitudinal IRT analysis is a novel statistical method highly applicable to PD clinical trials. It addresses limitations of traditional linear regression approaches and previous IRT investigations that either applied cross-sectional IRT models to longitudinal data or failed to estimate all parameters simultaneously. It is particularly useful because it can separate nontremor and tremor changes both over time and in response to treatment interventions.Item Open Access Resolving Missing Data from the Movement Disorder Society Unified Parkinson's Disease Rating Scale: Implications for Telemedicine.(Movement disorders : official journal of the Movement Disorder Society, 2022-06-18) Luo, Sheng; Goetz, Christopher G; Choi, Dongrak; Aggarwal, Sanket; Mestre, Tiago A; Stebbins, Glenn TBackground
Telemedicine has become standard in clinical care and research during the coronavirus disease 2019 pandemic. Remote administration of Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III (Motor Examination) precludes ratings of all items, because Rigidity and Postural Stability (six scores) require in-person rating.Objective
The objective of this study was to determine imputation accuracy for total-sum and item-specific MDS-UPDRS Motor Examination scores in remote administration.Methods
We applied multivariate imputation by chained equations techniques in a cross-sectional dataset where patients had one MDS-UPDRS rating (International Translational Program, n = 8,588) and in a longitudinal dataset where patients had multiple ratings (Rush Program, n = 396). Successful imputation was stringently defined as (1) generalized Lin's concordance correlation coefficient >0.95, reflecting near-perfect agreement between total-sum score with complete data and surrogate score, calculated without patients' actual Rigidity and Postural Stability scores; and (2) perfect agreement for item-level scores for Rigidity and Postural Stability items.Results
For total-sum score when Rigidity and Postural Stability scores were withdrawn, using one or multiple visits, multivariate imputation by chained equations imputation reached near-perfect agreement with the original total-sum score. However, at the item level, the degree of perfect agreement between the surrogate and actual Rigidity items and Postural Stability scores always fell below threshold.Conclusions
The MDS-UPDRS Part III total-sum score, a key clinical outcome in research and in clinical practice, can be accurately imputed without the Rigidity and Postural Stability items that cannot be rated by telemedicine. No formula, however, allows for specific item-level imputation. When Rigidity and Postural Stability item scores are of key clinical or research interest, patients with PD must be scored in person. © 2022 International Parkinson and Movement Disorder Society.Item Open Access Validation of the Kazakh version of the movement disorder Society-Unified Parkinson's disease rating scale(Clinical Parkinsonism and Related Disorders, 2024-01-01) Abdraimova, Saltanat; Myrzayev, Zhanybek; Karimova, Altynay; Talgatkyzy, Altynay; Khaibullin, Talgat; Kaishibayeva, Gulnaz; Elubaeva, Sandugash; Esembekova, Karlygash; Choi, Dongrak; Martinez-Martin, Pablo; Goetz, Christopher G; Stebbins, Glenn T; Luo, Sheng; Shashkin, Chingiz; Zharkinbekova, Nazira; Kaiyrzhanov, RauanBackground and Purpose: The International Movement Disorder Society revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) is widely used in the assessment of the severity of Parkinson's disease (PD). This study aimed to validate the Kazakh version of the MDS-UPDRS, explore its dimensionality, and compare it to the original English version. Methods: The validation was conducted in three phases: first, the English version of the MDS-UPDRS was translated into Kazakh and thereafter back-translated into English by two independent teams; second, the Kazakh version underwent a cognitive pretesting; third, the Kazakh version was tested in 360 native Kazakh-speaking PD patients. Both confirmatory and exploratory factor analyses were performed to validate the scale. We calculated the comparative fit index (CFI) for confirmatory factor analysis and used unweighted least squares for exploratory factor analysis. Results: The CFI was higher than 0.90 for all parts of the scale, thereby meeting the pre-set threshold for the official designation of a validated translation. Exploratory factor analysis also showed that the Kazakh MDS-UPDRS has the analogous factors structure in each part as the English version. Conclusions: The Kazakh MDS-UPDRS had a consistent overall structure as the English MDS-UPDRS, and it was designated as the official Kazakh MDS-UPDRS, which can reliably be used in the Kazakh-speaking populations. Presently, Kazakhstan stands as the sole country in both Central Asia and Transcaucasia with an MDS-approved translated version of the MDS-UPDRS. We expect that other Central Asian and Transcaucasian countries will embark on the MDS Translation Program for MDS-UPDRS in the near future.