The Dyskinesia Impairment Scale, Second Edition: Development, construct validity, and reliability.

Area of Science:

• Neurology
• Movement Disorders
• Clinical Assessment Tools

Background:

• Dystonia and choreoathetosis are complex movement disorders requiring accurate assessment.
• Existing scales like the Dyskinesia Impairment Scale (DIS) can be time-consuming.
• A need exists for a more user-friendly and efficient assessment tool.

Purpose of the Study:

• To develop and validate a shortened, user-friendly Second Edition of the Dyskinesia Impairment Scale (DIS-II).
• To evaluate the construct validity and reliability of the DIS-II for assessing dystonia and choreoathetosis.

Main Methods:

• Scale development involved expert consensus (n=21) and research group discussions (n=6).
• Rasch measurement model analysis was applied to DIS scores from 123 individuals with dyskinetic cerebral palsy or inherited/idiopathic dystonia.
• Construct validity and reliability were assessed using predefined quality criteria.

Main Results:

• The DIS-II assesses dystonia and choreoathetosis in action and rest across 11 body regions, with reduced scoring items (88 vs. 144) and videos (14 vs. 26).
• Rasch analysis confirmed good construct validity and excellent reliability, with the scale distinguishing eight ability levels.
• The DIS-II demonstrated superior interval properties compared to the DIS.

Conclusions:

• The DIS-II is a valid and reliable measure for dystonia and choreoathetosis.
• The DIS-II significantly reduces administration and scoring time compared to the original DIS.
• The interval-level data from DIS-II enhances longitudinal and inter-individual comparisons in clinical and research settings.