The relative sensitivity of the clinical global impressions scale and the brief psychiatric rating scale in antipsychotic drug trials

Although the Clinical Global Impression (CGI) and the Brief Psychiatric Rating Scale (BPRS) are both frequently used in drug trials for schizophrenia, their relative sensitivity in detecting differences between antipsychotics has not yet been examined. We therefore reanalyzed original patient data from all four pivotal, randomized controlled studies (n = 1205) that compared amisulpride with haloperidol in patients with schizophrenia. The sensitivity of the BPRS vs the CGI-improvement and the CGI-severity scales in detecting between-drug differences was estimated by calculating effect sizes and their 95% confidence intervals for both continuous (standardized mean differences) and dichotomous outcomes (odds ratios). The primary end points were the last observation carried forward results at study end points pooling all studies, but the results of the observed cases at different study weeks and the results of the single studies were also examined. The effect sizes derived from the BPRS and from the CGI were similar. When the single studies were pooled, all outcomes analyzed showed a statistically significant superiority of amisulpride compared to haloperidol as early as 2 weeks after initiation of treatment. The CGI may be as sensitive as the BPRS in detecting efficacy differences between antipsychotic drugs, although specific studies with truly independent ratings would be needed for confirmation. The fact that it takes only 1-2 min to fill in the CGI justifies its use in addition to more specific scales in drug trials for schizophrenia. Further development and evaluation of the CGI is warranted.