Rasch analysis of the Hospital Anxiety and Depression Scale (HADS) for use in motor neurone disease
- Equal contributors
1 Walton Centre for Neurology and Neurosurgery, Lower Lane, Liverpool, UK
2 Department of Psychology, The University of Liverpool, Bedford Street South, Liverpool, UK
3 Department of Neurology, Hope Hospital, Stott Lane, Greater Manchester, UK
4 Royal Preston Hospital, Sharoe Green Lane, Preston, UK
5 Sheffield Institute of Translational Neuroscience (SITraN), University of Sheffield, 385A Glossop Road Sheffield, UK
6 Department of Clinical Neurology, John Radcliffe Hospital, Oxford, UK
7 Academic Department of Rehabilitation Medicine, University of Leeds, Leeds General Infirmary, Leeds, UK
Health and Quality of Life Outcomes 2011, 9:82 doi:10.1186/1477-7525-9-82Published: 29 September 2011
The Hospital Anxiety and Depression Scale (HADS) is commonly used to assess symptoms of anxiety and depression in motor neurone disease (MND). The measure has never been specifically validated for use within this population, despite questions raised about the scale's validity. This study seeks to analyse the construct validity of the HADS in MND by fitting its data to the Rasch model.
The scale was administered to 298 patients with MND. Scale assessment included model fit, differential item functioning (DIF), unidimensionality, local dependency and category threshold analysis.
Rasch analyses were carried out on the HADS total score as well as depression and anxiety subscales (HADS-T, D and A respectively). After removing one item from both of the seven item scales, it was possible to produce modified HADS-A and HADS-D scales which fit the Rasch model. An 11-item higher-order HADS-T total scale was found to fit the Rasch model following the removal of one further item.
Our results suggest that a modified HADS-A and HADS-D are unidimensional, free of DIF and have good fit to the Rasch model in this population. As such they are suitable for use in MND clinics or research. The use of the modified HADS-T as a higher-order measure of psychological distress was supported by our data. Revised cut-off points are given for the modified HADS-A and HADS-D subscales.