Psychometric Properties and Validation of the Polish Version of the 12-Item World Health Organization Disability Assessment Schedule 2.0 in Patients with Huntington’s Disease

Background: Huntington’s disease is a progressive neurodegenerative disorder that usually manifests in adulthood and is inherited in an autosomal dominant manner. The main aim of the study was to assess the psychometric properties of the 12-item WHO Disability Assessment Schedule (WHODAS) 2.0 in studying the level of disability in people with Huntington’s disease. Method: This is a cross-sectional study that covered 128 people with Huntington’s disease living in Poland. We examined scale score reliability, internal consistency, convergent validity, and known-group validity. The disability and quality of life of people with Huntington’s disease were also assessed. Results: The scale score reliability of the entire tool for the research group was high. The Cronbach’s α test result for the whole scale was 0.97. Cronbach’s α for individual domains ranged from 0.95 to 0.79. Time consistency for the overall result was 0.99 and for particular domains ranged from 0.91 to 0.99, which confirmed that the scale was consistent over time. All of the 12-item WHODAS 2.0 domains negatively correlated with all of the Huntington Quality of Life Instrument (H-QoL-I) domains. All correlation coefficients were statistically significant at the level of p < 0.001. The results obtained in the linear regression model showed that with each subsequent point of decrease in BMI the level of disability increases by an average of 0.83 points on the 12-item WHODAS 2.0 scale. With each subsequent year of the disease, the level of disability increases by an average of 1.39 points. Conclusions: This is the first study assessing disability by means of the WHODAS 2.0 in the HD patient population in Poland, and it is also one of the few studies evaluating the validity of the WHODAS 2.0 scale in assessing the disability of people with HD in accordance with the recommendations of DSM-5 (R). We have confirmed that the 12-item WHODAS 2.0 is an effective tool for assessing disability and changes in functioning among people with Huntington’s disease.