George McNally1, Hugh Rickards2, Mike Horton3, David Craufurd4. 1. College of Medical and Dental Sciences, University of Birmingham, UK. 2. Department of Neuropsychiatry, The Barberry, Birmingham, UK. 3. Academic Department of Rehabilitation Medicine, Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, UK. 4. Faculty of Medicine and Human Sciences, Institute of Human Development, University of Manchester and Manchester Academic Health Science Centre, Manchester, UK.
Abstract
BACKGROUND: The short version of the Problem Behaviours Assessment (PBA-s) is the recommended outcome measure for behavioural symptoms in Huntington's disease. Rasch analysis was used to further investigate the measurement limitations of the PBA-s. OBJECTIVES: 1) To assess the psychometric properties of the 11 severity and frequency items within the PBA-s and 2) to determine the construct validity of using a total PBA-s score as a clinical outcome measure. METHODS: PBA-s data for 517 participants from Enroll-HD were included in the Rasch analysis. Separate analyses were conducted for the severity and frequency items of the PBA-s, using RUMM2030 software. Achieving fit to the model provides supporting evidence that all items contribute to a single underlying latent trait. This property is defined as internal construct validity. RESULTS: The total PBA-s severity score demonstrated several important limitations, including disordered response categories for all 11 severity items, local dependency and poor targeting. However, modifying the original five-point scoring system to a four-point system resulted in ordered response categories for seven of the severity items and achieved a good overall fit to the Rasch model. For the total PBA-s frequency score, fit to the model was not achieved even after amendments to the scoring system. CONCLUSIONS: This study suggests that with reduction to a four-point scoring system, the total PBA-s severity score may be considered a valid clinical outcome measure. This study also suggests limitations in the use of a total PBA-s frequency score.
BACKGROUND: The short version of the Problem Behaviours Assessment (PBA-s) is the recommended outcome measure for behavioural symptoms in Huntington's disease. Rasch analysis was used to further investigate the measurement limitations of the PBA-s. OBJECTIVES: 1) To assess the psychometric properties of the 11 severity and frequency items within the PBA-s and 2) to determine the construct validity of using a total PBA-s score as a clinical outcome measure. METHODS:PBA-s data for 517 participants from Enroll-HD were included in the Rasch analysis. Separate analyses were conducted for the severity and frequency items of the PBA-s, using RUMM2030 software. Achieving fit to the model provides supporting evidence that all items contribute to a single underlying latent trait. This property is defined as internal construct validity. RESULTS: The total PBA-s severity score demonstrated several important limitations, including disordered response categories for all 11 severity items, local dependency and poor targeting. However, modifying the original five-point scoring system to a four-point system resulted in ordered response categories for seven of the severity items and achieved a good overall fit to the Rasch model. For the total PBA-s frequency score, fit to the model was not achieved even after amendments to the scoring system. CONCLUSIONS: This study suggests that with reduction to a four-point scoring system, the total PBA-s severity score may be considered a valid clinical outcome measure. This study also suggests limitations in the use of a total PBA-s frequency score.
Entities:
Keywords:
Enroll-HD; Huntington’s disease; Problem Behaviours Assessment; Rasch; psychometrics
Authors: Verena Baake; Emma M Coppen; Erik van Duijn; Eve M Dumas; Simon J A van den Bogaard; Rachael I Scahill; Hans Johnson; Blair Leavitt; Alexandra Durr; Sarah J Tabrizi; David Craufurd; Raymund A C Roos Journal: Neuroimage Clin Date: 2018-03-27 Impact factor: 4.881
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