Noninferiority of perphenazine vs. three second-generation antipsychotics in chronic schizophrenia

Noninferiority analysis is a statistical method of growing importance in comparative effectiveness research that has rarely been used in psychopharmacology. This method is used here to evaluate whether first-generation antipsychotics are clinically not inferior to second-generation antipsychotics (SGAs) using data from the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE). A conservative noninferiority margin (NIM) on the Positive and Negative Syndrome Scale (PANSS) was derived from the smallest published value for the minimal clinically important difference, further reduced by 25%. This NIM was used to assess whether perphenazine is noninferior to olanzapine, risperidone, and quetiapine on the basis of the 95% confidence intervals of differences in mean PANSS outcomes (N = 1049). Perphenazine was noninferior to all three SGAs during 18 months of intention-to-treat analysis and in several subanalyses. Noninferiority can be evaluated from studies designed as superiority trials. Power was available in the CATIE to conduct noninferiority analysis.