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

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

INTRODUCTION

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by declines in cognitive and functional severities. This research utilized the Clinical Dementia Rating (CDR) to assess the influence of tilavonemab on these deteriorations.

METHODS

Longitudinal Item Response Theory (IRT) models were employed to analyze CDR domains in early-stage AD patients. Both unidimensional and multidimensional models were contrasted to elucidate the trajectories of cognitive and functional severities.

RESULTS

We observed significant temporal increases in both cognitive and functional severities, with the cognitive severity deteriorating at a quicker rate. Tilavonemab did not demonstrate a statistically significant effect on the progression in either severity. Furthermore, a significant positive association was identified between the baselines and progression rates of both severities.

DISCUSSION

While tilavonemab failed to mitigate impairment progression, our multidimensional IRT analysis illuminated the interconnected progression of cognitive and functional declines in AD, suggesting a comprehensive perspective on disease trajectories.

Highlights

Utilized longitudinal Item Response Theory (IRT) models to analyze the Clinical Dementia Rating (CDR) domains in early-stage Alzheimer's disease (AD) patients, comparing unidimensional and multidimensional models.Observed significant temporal increases in both cognitive and functional severities, with cognitive severity deteriorating at a faster rate, while tilavonemab showed no statistically significant effect on either domain's progression.Found a significant positive association between the baseline severities and their progression rates, indicating interconnected progression patterns of cognitive and functional declines in AD.Introduced the application of multidimensional longitudinal IRT models to provide a comprehensive perspective on the trajectories of cognitive and functional severities in early AD, suggesting new avenues for future research including the inclusion of time-dependent random effects and data-driven IRT models.

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

Background

Minimum clinically important difference (MCID) is the smallest change in an outcome measure that is considered clinically meaningful. Using validated MCID thresholds for outcomes powers trials adequately to detect meaningful treatment effects, aids in their interpretation and guides development of new outcome measures.

Objectives

To provide a comprehensive summary of MCID thresholds of various symptom severity scales reported in movement disorder.

Methods

We conducted systematic review of the literature and included studies of one or more movement disorders, and reporting MCID scales.

Results

2763 reports were screened. Final review included 32 studies. Risk of bias (RoB) assessment showed most studies were of good quality. Most commonly evaluated scale was Unified Parkinson's Disease Rating Scale (UPDRS) (11 out of 32). Four studies assessing MDS-UPDRS had assessed its different sub-parts, reporting a change of 2.64,3.05,3.25 and 0.9 points to detect clinically meaningful improvement and 2.45,2.51,4.63 and 0.8 points to detect clinically meaningful worsening, for the Part I, II, III and IV, respectively. For Parts II + III, I + II + III and I + II + III + IV, MCID thresholds reported for clinically meaningful improvement were 5.73, 4.9, 6.7 and 7.1 points respectively; while those for clinically meaningful worsening were 4.7, 4.2, 5.2 and 6.3 points, respectively. MCID thresholds reported for other scales included Abnormal Involuntary Movement Scale (AIMS), Toronto Western Spasmodic Torticollis Rating Scale (TWSRS), and Burke-Fahn-Marsden Dystonia Scale (BFMD).

Conclusion

This review summarizes all the MCID thresholds currently reported in Movement disorders research and provides a comprehensive resource for future trials, highlighting the need for standardized and validated MCID scales in movement disorder research.

The Tardive Dyskinesia Impact Scale (TDIS), a novel patient-reported outcome measure in tardive dyskinesia: development and psychometric validation

BACKGROUND

Tardive dyskinesia (TD), a movement disorder in which patients experience abnormal involuntary movements, can have profound negative impacts on physical, cognitive, and psychosocial functioning. The Abnormal Involuntary Movement Scale (AIMS), a clinician-rated outcome, is considered the gold standard for evaluating treatment efficacy in TD clinical trials. However, it provides little information about the impacts of uncontrolled movements from a patient perspective and can be cumbersome to administer in clinical settings. The Tardive Dyskinesia Impact Scale (TDIS) was developed as a patient-reported outcome measure to fulfill the need for a disease-specific impact assessment in TD. The objective of the present study was to develop and evaluate the psychometric properties of the TDIS to determine whether it is fit-for-purpose to measure TD impact.

METHODS

Data from qualitative studies and phase 3 trials of a VMAT2 inhibitor for the treatment of TD (KINECT3 and KINECT4) were used to determine the psychometric properties of the TDIS. Qualitative research included concept elicitation and cognitive debriefing interviews with TD patients and their caregivers in order to assess how well the TDIS captured key domains of TD impact. Quantitative analyses to examine the psychometric properties of the TDIS included assessing construct validity (factor structure, known groups, and predictive validity) and responsiveness to change.

RESULTS

Qualitative results showed that the TDIS captures the key TD impacts reported by patients and caregivers and that the TDIS was interpreted as intended and relevant to patients' experiences. Quantitative results found evidence of 2 underlying domains of the TDIS: physical and socioemotional (Comparative Fit Index > 0.9). Known groups and predictive validity indicated that, compared with the AIMS, the TDIS captures unique content (correlation between AIMS and TDIS = 0.2-0.28). The TDIS showed responsiveness to change in treatment, with TDIS scores improving over 48 weeks in the 2 phase 3 trials.

CONCLUSIONS

The TDIS captures relevant information about the impact of TD and is easily administered in a clinician's office or patient's home. It may be used longitudinally to show changes in TD burden over time. The TDIS complements the AIMS; using these assessments together provides a more holistic assessment of TD.

Development, Efficacy and Safety of Once-daily, Bedtime, Extended-release Amantadine (Gocovri®) to Treat Dyskinesia and OFF Time in Parkinson’s Disease

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Successful use of the Unified Dyskinesia Rating Scale regardless of PD- or dyskinesia-duration

OBJECTIVE

We assessed differential item functioning (DIF) in the Unified Dyskinesia Rating Scale (UDysRS) to evaluate bias risk from the duration of Parkinson's Disease (PD) and duration of dyskinesia.

BACKGROUND

Assessing DIF is a core validation step for rating scales. If DIF is present for an item, interpretation must consider influences from the tested covariates. DIF can be uniform or non-uniform, depending on the consistency of influence from the given covariate across all levels of dyskinesia.

METHODS

Using a large UDysRS database (N = 2313), uniform and non-uniform DIF related to the duration of PD and/duration of dyskinesia were tested. Unidimensionality of UDysRS was first confirmed using confirmatory factor analysis. DIF analysis was conducted using two independent latent models. DIF in an item was confirmed if both methods independently identified DIF at a significance level using Bonferroni correction. McFadden pseudo R^2 measured clinical relevancy of DIF magnitude (negligible, moderate, and large) for items identified with DIF, and items with DIF were considered clinically relevant if they exceeded a negligible designation.

RESULTS

Most items did not show uniform or non-uniform DIF based on PD and dyskinesia duration in isolation or in combination. For all items where DIF was identified, the magnitude statistic was in the negligible range (McFadden pseudo R^2 < 0.035) and the combined impact of multiple identified DIF items on UDysRS likewise did not exceed the negligible designation.

CONCLUSION

The absence of clinically relevant DIF suggests that the UDysRS can be applied across all patients regardless of their PD- or dyskinesia-duration.

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

BACKGROUND

Motor complications represent an important clinical problem in the treatment of Parkinson's disease (PD). The Motor Complications Part of the Movement Disorder Society-sponsored Unified Parkinson's Disease Rating Scale (MDS-UPDRS Part IV) and the Unified Dyskinesia Rating Scale (UDysRS) are among the most reliable instruments to evaluate these problems. The minimal clinically important difference thresholds are the smallest changes in the outcome measures that are clinically meaningful.

AIMS

The aim of our study was to calculate the minimal clinically important difference thresholds for the MDS-UPDRS Part IV and the historic parts of the UDysRS.

METHODS

A total of 1044 paired investigations of 436 patients were analyzed. Changes in the respective outcome measures (MDS-UPDRS Part IV, UDysRS Parts I and II) were compared to the Patient-rated Global Impression of Improvement scores (anchors). Subsequently, we applied receiver-operating characteristic analysis to ascertain the MCID thresholds with optimal sensitivity and specificity.

RESULTS

Any improvement greater than 2.1 points or any worsening greater than 1.8 points on UDysRS Part I represents a minimal, yet clinically meaningful change. In reference to UDysRS Part II, the smallest changes considered clinically relevant are 1.8 and 1.7 points for improvement and deterioration, respectively. The thresholds for the MDS-UPDRS Part IV are 0.9 points for improvement and 0.8 points for worsening.

CONCLUSIONS

Our estimates may allow the judgment of the clinical relevance of numeric changes in the dyskinesia scales.