Objective: To validate the proposed XDP-MDSP (X-linked dystonia-parkinsonism – The Movement Disorder Society of the Philippines) rating scale in patients clinically diagnosed to have XDP.

Background: X-Linked Dystonia Parkinsonism (XDP, DYT3) is an adult-onset, degenerative movement disorder endemic to Panay Island. We developed the XDP-MDSP rating scale to classify patients as to extent and severity of disease, track their progression, and determine response to treatment.

Methods: The proposed scale was administered to patients with a clinical diagnosis of XDP. Each patient was evaluated by one rater. After the XDP-MDSP scale was completed, the following were done by the same examiners to determine construct validity by correlating the different parts of the scale with the following validated scales: Burke-Fahn-Marsden dystonia scale, UPDRS Motor scale, NMSQuest scale, and SCOPA-ADL scale. Divergent validity was determined by correlating the scale with the Hamilton Anxiety and Depression scale and the Mini-Mental Status Exam.

Results: A total of 204 patients were recruited to the study. Cronbach’s alpha for the entire 5-part scale was acceptable at 0.805. Inter-domain correlation for the first four parts of the scale measuring four different domains (dystonia, parkinsonism, non-motor features, and activities of daily living) was acceptable with ranges from 0.434 to 0.671; the correlation between these domains and the last (global rating) was slightly lower at 0.319 to 0.447. Convergent validity was tested by performing Pearson correlation with other scales: Part I and BFM; Part II and UPDRS; Part III and NMS; and Part IV and SCOPA. Correlation was acceptable with values ranging from 0.323 to 0.428. Divergent validity was tested by performing Pearson correlation with three other scales: MMSE, HADS-P, and HAMD. There was significant correlation between the scale and HADS-P and HAMD.

Conclusions: The proposed XDP-MDSP scale is internally valid, although the last domain (global rating) may have to be modified slightly due to lower correlation with the other domains. Since Pearson correlation is acceptable, there is also convergent validity. On the other hand, the significant correlation between the proposed scale and the HADS-P and HAMD may be due to the fact that many patients also have concomitant anxiety and depression. Another scale can perhaps be used to measure divergent validity.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/validation-of-the-xdp-mdsp-rating-scale-for-the-evaluation-of-patients-with-x-linked-dystonia-parkinsonism-xdp/