Noninferiority trial design and analysis with an ordered three-level categorical endpoint.

This paper extends standard methodology for noninferiority trial design from a binary endpoint to an ordered three-level endpoint, such as "success," "intermediate," and "failure." A metric that summarizes outcome on this endpoint is proposed, and the corresponding sample size requirements are presented. This ordered endpoint can be collapsed into two different binary endpoints, respectively lumping "intermediate" outcomes with "success" or with "failure." We describe how the ordered three-level endpoint compares with these two binary endpoints with respect to the noninferiority margin and sample size requirements.