A cost-effectiveness clinical decision analysis model for schizophrenia.

A model was developed to estimate the medical costs and effectiveness outcomes of three antipsychotic treatments (olanzapine, haloperidol, and risperidone) for patients with schizophrenia. A decision analytic Markov model was used to determine the cost-effectiveness of treatments and outcomes that patients treated for schizophrenia may experience over a 5-year period. Model parameter estimates were based on clinical trial data, published medical literature, and, when needed, clinician judgment. Direct medical costs were incorporated into the model, and outcomes were expressed by using three effectiveness indicators: the Brief Psychiatric Rating Scale, quality-adjusted life years, and lack of relapse. Over a 5-year period, patients on olanzapine had an additional 6.8 months in a disability-free health state based on Brief Psychiatric Rating Scale scores and more than 2 additional months in a disability-free health state based on quality-adjusted life years, and they experienced 13% fewer relapses compared with patients on haloperidol. The estimated 5-year medical cost associated with olanzapine therapy was $1,539 less than that for haloperidol therapy. Compared with risperidone therapy, olanzapine therapy cost $1,875 less over a 5-year period. Patients on olanzapine had approximately 1.6 weeks more time in a disability-free health state (based on Brief Psychiatric Rating Scale scores) and 2% fewer relapses compared with patients on risperidone. Sensitivity analyses indicated the model was sensitive to changes in drug costs and shortened hospital stay. Compared with both haloperidol and risperidone therapy, olanzapine therapy was less expensive and provided superior effectiveness outcomes even with conservative values for key parameters such as relapse and discontinuation rates.