Dutch translation, adaptation and validation of the OT-10 scale for orthostatic tremor

Introduction: There are currently no effective treatments for primary orthostatic tremor (POT). An adequate disease-specific POT severity scale is a prerequisite to conduct clinical trials and monitor disease severity in clinical practice. Recently, the English OT-10 scale has been developed for this purpose. Here we aimed to obtain a scale to measure the severity of POT in Dutch speaking individuals. Methods: An established translation, adaptation and validation approach was employed to obtain a Dutch version of the OT-10 scale. Validation was performed in a Dutch POT cohort (n = 46). Results: A Dutch OT-10 scale was obtained which showed good internal consistency (Cronbach's alpha > 0.80), total score test–retest reliability (intraclass correlation coefficient > 0.80), and concurrent validity (Pearson correlation > 0.80). Item-to-total correlation was good (weighted kappa > 0.40) for all items, and item test–retest reliability was good (weighted kappa > 0.40) for eight out of ten items. Overall, the Dutch OT-10 scale demonstrated acceptable validity. Conclusions: We obtained and validated a Dutch version of the OT-10 scale, capturing POT severity. Next to its use in clinical practice, translation and validation of the OT-10 scale in more languages will help to find evidence-based treatments for POT.