The Calgary Depression Rating Scale for Schizophrenia: Development and Interrater Reliability of a German Version (CDSS-G)

A German version of the Calgary Depression Rating Scale for Schizophrenia (CDSS-G) approved by the author of the original scale is presented comprising a semi-structured interview for 9 items to sensitively and specifically assess depression in schizophrenia and related disorders. The process of translation is outlined and the finally derived CDSS-G was investigated with respect to interrater reliability in three studies. To keep comparability with the CDSS source version a standard procedure was used. Two trained raters jointly assessed ten schizophrenic patients (study I). In a second study, videotapes with the CDSS-G were presented to clinically inexperienced raters (study II, N = 14/15) to test the agreement on the CDSS-G in this sample. Finally, in a third study clinically experienced researchers participated in a rater training (study III, N = 34). They carried out CDSS ratings on three patients with mild depressive symptoms. The dependence of interrater reliability on depression severity was investigated for all studied patients. Both intraclass correlation coefficients (ICC) and weighted kappa coefficients (kappa(w)) were calculated. The results revealed a high ICC = 0.97 in study I for the total CDSS-G score. Single item ICC values were all above 0.70. The results of study II revealed somewhat lower agreement on CDSS-G items and total scores in psychiatric novices with however acceptable values of kappa(w)>0.50 for the total scores. Study III yielded satisfactory results (0.66<kappa(w)<0.76) for clinically experienced psychiatrists in schizophrenic patients with mild depression. The results demonstrate adequate to excellent interrater reliability of the CDSS-G corroborating the results of the original version in different settings.