Existing anxiety rating scales have limited construct validity in patients with Parkinson's disease (PD). This study was undertaken to develop and validate a new anxiety rating scale, the Parkinson Anxiety Scale (PAS), that would overcome the limitations of existing scales. The general structure of the PAS was based on the outcome of a Delphi procedure. Item selection was based on a canonical correlation analysis and a Rasch analysis of items of the Hamilton Anxiety Rating Scale (HARS) and the Beck Anxiety Inventory (BAI) from a previously published study. Validation was done in a cross-sectional international multicenter study involving 362 patients with idiopathic PD. Patients underwent a single screening session in which the PAS was administered, along with the Hamilton Depression Rating Scale, the HARS, and the BAI. The Mini International Neuropsychiatric Interview was administered to establish Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnoses of anxiety and depressive disorders. The PAS is a 12-item observer or patient-rated scale with three subscales, for persistent, episodic anxiety and avoidance behavior. Properties for acceptability and reliability met predetermined criteria. The convergent and known groups validity was good. The scale has a satisfactory factorial structure. The area under the receiver operating characteristics curve and Youden index of the PAS are higher than that of existing anxiety rating scales. The PAS is a reliable and valid anxiety measure for use in PD patients. It is easy and brief to administer, and has better clinimetric properties than existing anxiety rating scales. The sensitivity to change of the PAS remains to be assessed.
Keywords: Parkinson's disease; anxiety; depression; rating scale; ‘non-motor’ symptoms.
© 2014 International Parkinson and Movement Disorder Society.