Dimensions of the Brief Psychiatric Rating Scale: an examination of stability during haloperidol treatment.
The purpose of the study was to investigate invariance of the factor structure of the Brief Psychiatric Rating Scale (BPRS) during haloperidol treatment. Data were collected in a placebo-controlled, double-blind, crossover treatment study examining the relationship between haloperidol plasma level and clinical outcome. Subjects were 173 acutely exacerbated, newly admitted patients with a diagnosis of schizophrenia or schizoaffective disorder. Exploratory (EFA) and confirmatory (CFA) factor analyses were performed at four time points: (1) last day of the preplacebo period; (2) last day of the placebo period; (3) end of the first treatment week; and (4) end of the treatment period. EFAs demonstrated (1) good reproducibility of commonly used BPRS factors at the preplacebo time point, (2) substantial changes in the factor structure during the placebo period, and (3) a reemergence of the initial (preplacebo) factor structure for most of the factors during haloperidol treatment. CFAs showed that traditional clinical factors were correlated with each other at all time points and that there were substantial changes in correlation among these factors over time. Our results suggest that longitudinal applications of traditional BPRS subscales should take factorial stability over time into consideration. Since many clinical trials use placebo data as a standard for longitudinal comparisons, further psychometric investigation is necessary to increase construct reliability and temporal stability.