Objective:

We aimed to cross-validate the Orthostatic Tremor Severity and Disability Scale (OT-10) by comparing it to four different assessments: the Activities-specific Balance Confidence Scale (ABC), Dizziness Handicap Inventory (DHI), Short Form Health Survey (SF-36), and the Clinical Global Impression Scale of Severity (CGI-S). 

Background:

Orthostatic Tremor (OT) is a rare and debilitating movement disorder characterized by 13-18 Hz leg tremors and unsteadiness upon standing that alleviates when walking or sitting. The OT-10 scale was created in 2020 to objectively assess symptom severity in OT patients, and to be used as possible studies end-point. However, the scale has not undergone convergence validation. 

Design/Methods:

Data collected prospectively and simultaneously from 16 OT patients (12 female) for all five scales. Mean age 70 years (48-80 yrs). Mean disease duration 19 years (5-60 yrs). Final scores from the OT-10 were compared to the ABC, DHI, SF-36, and CGI-S scores using correlation and regression analysis to determine the relationship and similarity between the scales. Correlations were calculated using a Pearson Correlation Test.  

Results:

The ABC, DHI, SF-36, and CGI-S were found to strongly predict the OT-10 scores (R² = 0.7, F(4) = 7.86, p = 0.003). The OT-10 has a strong significant relationship with the ABC (r = -0.72, p = 0.002) and the CGI-S (r = 0.51, p = 0.04), but has nonsignificant relationships with the DHI (r = -0.34, p = 0.198) and SF-36 (r = -0.40, p = 0.182). We further discuss the likely explanations of these relationships, in particular as it relates to balance specificity.  

Conclusions:

Our study provides convergence validation data for the use of the OT-10 scale. Future studies should focus on the development and validation of translated versions of the scale.