Assessment of dementia in elderly schizophrenics with structured rating scales

Although a number of elderly institutionalized schizophrenic patients appear to suffer from dementia, little is known about the characteristics of the cognitive impairment or its prevalence in this population. In order to answer these questions it is necessary to first reliably and validly assess dementia in elderly schizophrenic patients. This paper reports the results of a study examining the reliability of assessments of the severity of dementia in schizophrenia using scales designed for other dementing conditions and examining the convergence of ratings of the severity of dementia generated from all available sources of information (patient, caregiver, and chart) versus the chart alone. It was found that the interrater reliability of these ratings was very high. On the other hand ratings generated from the hospital chart alone, without contact with either the patient or caregiver, manifested a systematic bias toward overestimation of the severity of dementia. These results suggest that dimentia assessment in schizophrenia does not require different instrumentation from that used in other conditions but that relying on the medical chart alone would induce a systematic bias in the results.