Study designs of evaluations included in the review
The inclusion criteria were not specified in terms of study design. However, it appears that the included studies were randomised controlled trials (RCTs). The duration of the included studies ranged from 6 weeks to 2 years.
Specific interventions included in the review
Studies comparing clozapine with conventional antipsychotics were eligible for inclusion. The included studies compared clozapine (176 to 600 mg/day) with the following antipsychotics: chlorpromazine (600 to 1,200 mg/day), haloperidol (16 to 28 mg/day), or usual care with 1,386 chlorpromazine equivalents.
Participants included in the review
Studies of patients with treatment-resistant schizophrenia were included in the review. The included studies used different definitions of treatment resistance. All but one study included patients who had failed to respond to at least two conventional antipsychotic drugs. Some studies defined failure to respond as serious difficulty in functioning, symptoms moderate or above on the Brief Psychiatric Rating Scale (BPRS), or as both of these conditions; other studies did not define this term. At baseline, the patients' BPRS scores ranged from 38 to 84. The studies included children and adults (including patients aged older than 55 years). Most studies were of patients who had been hospitalised for between 9 months and 18 years. Two studies were of out-patients.
Outcomes assessed in the review
The inclusion criteria were not specified in terms of outcomes. The main outcome in the review was the symptom score at the end of the study, or the change in symptoms. All of the included studies assessed symptoms using either the BPRS or the Positive and Negative Syndrome Scale (PANSS). The review also assessed rates of hospitalisation and discharge, and withdrawal rates.
How were decisions on the relevance of primary studies made?
The author did not state how the papers were selected for the review, or how many reviewers performed the selection.