Validity of a Brazilian version of the Zung self-rating depression scale for screening of depression in patients with Parkinson's disease.

INTRODUCTION

Parkinson's disease (PD) is a neurodegenerative disorder with prominent motor manifestations and many other non-motor symptoms that significantly decrease quality-of-life and are frequently under-recognized, for example depression.

OBJECTIVE

To study the validity of a Brazilian version of the Zung Self-rating Depression Scale (SDS) for the diagnosis of depression in patients with PD.

METHODS

We evaluated 78 consecutive non demented patients over the age of 40 with diagnosis of PD at a Movement Disorders Outpatient Clinic, who could read and understand questionnaires. They completed the SDS and the Geriatric Depression Scale with 15 items (GDS-15). The diagnosis of depression was made after a structured clinical interview based on DSM-IV criteria for the diagnosis of major depression (SCID-CV).

RESULTS

The prevalence of major depression was 23.1%. Cronbach's alpha was 0.73 and the area under the ROC curve was 0.93 for the SDS. The score index of 55 had a sensitivity of 88.9% and a specificity of 83.3% for the diagnosis of depression. The total scores of the SDS and GDS-15 were highly correlated (0.652, p < 0.0001) and correlated weakly with the scores of a motor scale.

DISCUSSION

The SDS is a valid tool for screening depression in patients with PD since the specific SDS index of 55 is adopted. Two shortened versions could be used with good results.