A Study on the Reliability and Validity of the Korean Version of the Calgary Depression Scale for Schizophrenia(K-CDSS)

Kim, Yong Ku; Won, Seong Doo; Lee, Kyoung Min; Choi, Hyun Seok; Jang, Hong Seok; Lee, Bun Hee; Han, Chang Su

Abstract

OBJECTIVES
This study was performed to standardize the Korean Version of Calgary Depression Scale for Schizophrenia (K-CDSS), a semi-structured interview scale to assess depression in schizophrenia patients and to determine the psychometric properties and clinical utility of the K-CDSS.
METHODS
Sixty-one patients diagnosed as schizophrenia by DSM-IV criteria were recruited in this study. Then, the patients were interviewed using the Structure Clinical Interview for DSM-IV (SCID) by a trained psychologist. Subsequently, the KCDSS, Positive and Negative Syndrome Scale (PANSS), Hamilton Depression Rating Scale (HDRS), Montgomery-Asberg Depression Rating Scale (MADRS) and Simpson Angus Rating Scale (SAS) were administered by a psychiatrist. Lastly, the K-CDSS was re-assessed by a second independent rater without any previous information of patients to confirm the inter-rater reliability.
RESULTS
The internal consistency using Cronbach's alpha was 0.852. Inter-rater reliability using Intraclass Correlation Coefficient (ICC) for single items and for sum score were 0.659-0.889 and 0.963, respectively. K-CDSS was assessed by a second Factor analysis and ROC (receiver operating characteristic) curve analysis were conducted. The factor analysis revealed a single factor that accounted for 53.7% of the total variance, suggesting that the uni-dimensional structure of the K-CDSS may be retained. In addition, K-CDSS showed a good convergent validity with very strong correlations with HDRS (r=0.75) and MADRS (r=0.81), respectively. However, K-CDSS was not correlated with PANSS-positive, PANSS-negative and SAS, demonstrating its satisfactory discriminant validity. The area under the ROC curve was 0.968 (standard error=0.036, p<.001). With a cut-off point of 8, the K-CDSS had a sensitivity 83.3%, specificity 97.9%, positive predictive value 90.9% and negative predictive value 95.8%.
CONCLUSION
K-CDSS is considered as a short and valid tool to identify depressive symptoms in schizophrenia.