Schizophrenia, Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) and number needed to treat: how can CATIE inform clinicians?

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The schizophrenia medication study conducted as part of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) provided a large quantity of data. However, placing these data into a clinically meaningful context for the individual practitioner has been challenging. Effectiveness and safety outcome data were extracted from the three principal publications that documented the results of phases 1 and 2 of the CATIE schizophrenia study. Number needed to treat (NNT) and number needed to harm (NNH) were calculated from the categorical results, together with their confidence intervals. Olanzapine and clozapine demonstrated advantages over comparators in terms of all-cause discontinuation, largely driven by efficacy advantages. NNT for olanzapine compared with perphenazine, quetiapine, risperidone and ziprasidone ranged from 5.5 to 10.1 in phase 1. NNT for clozapine compared with risperidone or quetiapine was approximately 3 in phase 2. There were marked differences in association with weight gain and metabolic effects, with olanzapine demonstrating a NNH ranging from 12.4 to 17.7 in terms of discontinuation of treatment in phase 1 because of these effects. Results from phase 2 reflect phase 1 in this regard, and demonstrated an advantage for ziprasidone in terms of discontinuation because of weight gain or metabolic effects, with NNT ranging from 10.6 to 20.8. However, these notable differences in association with weight gain and metabolic effects did not seem to drive the differences in overall time to all-cause discontinuation. NNT and NNH can help place the wide array of CATIE results into clinical context, and permits quantification of the differences observed between the antipsychotics that were tested.

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