Development and clinimetric testing of the Unified Drug-Induced Movement Disorders Scale (UDIMS)

ObjectiveSeveral movement disorders develop secondary to the use of psychotropic drugs, for which multiple symptom rating scales are in common use. We planned to develop the Unified Drug-Induced Movement Scale (UDIMS) to assess the severity and impact of drug-induced dyskinesia, tremor, drug-induced parkinsonism, akathisia, dystonia and myoclonus with a single instrument. MethodsBased on a literature review, consultation and pilot work, a 12-item instrument was developed, with each item rated on a 0-4 scale. The clinimetric properties of UDIMS were examined in 53 psychiatric patients on psychotropic medications, using established ratings scales for validation. The factor structure of the scale was examined, and the movement disorder correlates of distress and disability were determined. ResultsThe instrument has good inter-rater reliability. Its correspondence with three other scales - Abnormal Involuntary Movements Scale, Simpson-Angus Scale and Prince Henry Hospital Akathisia Scale - for the relevant items was high. A principal components analysis yielded four factors, considered to represent tremor, parkinsonism, akathisia and dyskinesia. Overall movement-disorder related disability was related to parkinsonism and dyskinesia, while distress to all four components. ConclusionsUDIMS is a reliable and valid scale to quantify a range of drug-induced movement disorders (DIMDs), that obviates the need for the use of multiple rating scales. Its widespread use by both clinicians and researchers, and further refinement based on this, will help promote the detection and treatment of drug-induced movement disorders, thereby reducing both distress and disability.