PREDICTORS OF DIFFERENTIAL RESPONSE TO CLOZAPINE AND HALOPERIDOL

Background: We sought to identify baseline predictors of response to c lozapine. Methods: Data were from a 15-site randomized clinical trial comparing clozapine and haloperidol in hospitalized patients with refr actory Schizophrenia (n = 423). Three-month outcomes were analyzed wit h the full sample (n = 368 due to attrition). Because of crossovers, a nalyses of 12-month outcomes were conducted with crossovers excluded ( n = 291). Clinical predictors included age, I-ace, diagnosis (current substance abuse, paranoid subtype of schizophrenia, or depressive synd rome), severity of symptoms, quality of life, age at onset of schizoph renia, extrapyramidal symptoms, and VA compensation payment. Multiple regression analysis was used to examine the interaction of treatment c ondition and each of these variables in predicting outcomes for sympto ms, quality of life, side effects, and days hospitalized. Results: Pat ients with higher quality of life at baseline (p = .04) and higher sym ptoms (p = .02) had relatively smaller declines in hospital days at 6 months. In the 12-month sample patients with higher levels of symptoms had greater symptom reductions at 12 months (p = .03) and greater imp rovement in quality of life (p = .004). Conclusions: Although high lev els of symptoms were associated with greater improvement on clozapine, these findings are not robust enough to suggest that any specific, cl inically defined subgroup of refractory patients should be preferentia lly targeted for clozapine treatment. (C) 1998 Society of Biological P sychiatry.