Statistical Considerations for Non-Inferiority Trials

Non-inferiority analysis uses one-sided confidence intervals to test non-inferiority rather than superiority. The lower limit of the confidence interval should be above the selected non-inferiority margin to establish non-inferiority. The determination of the confidence interval size depends on whether a 2.5% or a 5% level of significance is selected. It is important to note that a non-inferiority trial is different from an equivalence trial, as demonstrating non-inferiority does not automatically imply equivalence. Moreover, the choice of non-inferiority margin significantly impacts the sample size, with smaller margins requiring larger sample sizes. Clinicians must carefully select the minimally important clinical difference to ensure realistic and meaningful trial design.