Objective: We aim to assess the psychometric properties of the Korean version of Hospital Anxiety and Depression Scale (HADS) in a sample of early-stage Parkinson’s disease (PD) patients using Rasch analysis.

Background: Item response theory (IRT), also known as modern test theory, presents a measurement model for the probability of each possible response to a test item. The Rasch model is one of the most widely used one-parameter logistic (1PL) IRT models in various clinimetric applications. The HADS is a 14-item patient-report assessment which have been applied to evaluate depression and anxiety symptoms in PD patients. However, few studies examined the HADS instrument within the patients with early-stage PD based on the IRT.

Methods: All study subjects met the diagnostic criteria of the UK Parkinson’s Disease Society Brain Bank. Patients has diagnosed after 1 month and within 1 years. Patients with vascular parkinsonism, atypical parkinsonian syndrome or patients < 40 years old were excluded. The unidimensionality, Rasch model fits, person-item distribution, separation reliability, and response category utility of the HADS instrument were statistically evaluated using WINSTEPS version 4.0.1 (Winsteps Inc., Chicago, IL, USA) with Andrich's rating scale model (RSM).

Results: Principal component analyses of residuals revealed that the HADS depression-subscale (HADS-D) and HADS anxiety-subscale (HADS-A) had unidimensionality, although the original form of the HADS (HADS-total) was not unidimensional. There were no disordered thresholds in the four-point Likert’s scales used for the HADS-D or that used for the HADS-A. The HADS-D and HADS-A had satisfactory item separation reliabilities (ISRs) and person separation reliabilities (PSRs). Rasch analysis showed that the ISR of HADS-D was 0.96 and its PSR was 0.75. HADS-A had an ISR of 0.96 and a PSR of 0.73.

Conclusions: The HADS-D and HADS-A subscale provide unidimensional measures of depression-anxiety affect in the patients with early-stage PD, and no statistical support for disordering of the polytomous response categories. The results of Rasch nalysis support the use of HADS-D and HADS-A subscales among early PD patients as linear metric patient-reported outcome.

References: 1. Forjaz MJ, How to evaluate validation data. In: Sampaio C, Goetz CG, Schrag A. editors. Rating scales in Parkinson’s disease: clinical practice and research. New York: Oxford University Press; 2012. p.16–41. 2. Forjaz MJ, Rodriguez-Blázquez C, Martinez-Martin P. Rasch analysis of the hospital anxiety and depression scale in Parkinson’s disease. Mov Disord 2009;24:526–32.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rasch-analysis-of-the-hospital-anxiety-and-depression-scale-among-patients-with-early-stage-parkinsons-disease/