The objective of this study was to investigate reliability and validity of the self rated 30 item Geriatric Depression Scale (GDS) in screening and diagnosis of depression in Parkinson's disease (PD). The study sample comprised 109 non-demented patients with PD admitted to the movement disorders outpatient unit. The reference diagnosis of depression was made according to DSM-IV criteria. Discriminant validity and internal consistency of the total scale were studied. Sensitivity, specificity, and positive and negative predictive values (PPV and NPV) were calculated for different cutoff scores. Receiver operating characteristics (ROC) analysis was also carried out. The sample comprised 56 patients with and 53 without depression. In the discriminant validity analysis, the mean total GDS score of subjects with depression was significantly higher compared with those without depression. The Cronbach's a score was 0.92 and the split half correlation coefficient 0.91. The cutoff score of 13/14 provided the highest sum of sensitivity and specificity level. The sensitivity of this cutoff score was 0.78 and specificity 0.85, while PPV was 0.84 and NPV 0.79. The area under the curve value in the ROC analysis was 0.891. Sensitivity and specificity analysis showed that cutoff scores of 8/9 or 9/10 could be useful for screening and 14/15 or 15/16 for diagnostic purposes. This study showed that the 30 item GDS, with its high discriminant validity, internal consistency, and reasonably clear cutoff scores, could be a useful screening or diagnostic self rated depression scale in patients with PD.

Our findings suggest that the 30-item GDS has high discriminant validity, internal consistency, and test-retest reliability and reasonably useful cutoff scores; thus it can be used as a screening tool for minor depression in the poststroke population.

Background and purpose – This study aims to investigate the validity and reliability of the Turkish Version of the 39-item Parkinson Disease Questionnaire. Methods – A total of 100 patients with Parkinson’s disease who were admitted to the outpatient neurology clinic in Koc University and Istanbul University were enrolled. 39- item Parkinson Disease Questionnaire, Parkinson Disease Quality of Life Questionnaire, Unified Parkinson’s Disease Rating Scale, Hoehn-Yahr Scale, and Short Form Health Survey-36 were administered to all participants. 39-item Parkinson Disease Questionnaire was repeated 2 weeks later. Results – The internal consistency coefficient of the 39-item Parkinson Disease Questionnaire was 0.957. Test-retest correlation ranged between r = 0.693-0.979. Reliability of Turkish version of the 39-item Parkinson Disease Questionnaire was found to be very high with the exclusion of one item (30th item). The scale was found to be consistent over time and correlated positively with Hoehn-Yahr Scale, and negatively with Unified Parkinson’s Disease Rating Scale, Parkinson Disease Quality of Life Questionnaire, and Short Form Health Survey-36. Conclusion – Turkish version of the 39-item Parkinson Disease Questionnaire, with the exclusion of the 30th item can be used reliably in assessing the quality of life of Parkinson’s patients.