Case identification and stability of the deficit syndrome of schizophrenia.

In certain situations, such as large epidemiological studies, it may be necessary to use proxy case-identification tools instead of "gold-standard" assessments. The deficit syndrome of schizophrenia requires a clinical assessment that may not be feasible in some study populations. Measures for the discrimination of deficit and nondeficit patients, based on the Brief Psychiatric Rating Scale (BPRS), were assessed in a group of 100 outpatients with chronic schizophrenia. A rationally based case-identification tool was validated, and its case-identification properties were found to be stable over time; consequently, this proxy measure may be of use in other data sets. The stability of the relationship between this BPRS measure and the deficit/nondeficit categorization supports the view that it is a valid categorization.