Sample size estimation for the averted events ratio.

ABSTRACT:

Background

The averted events ratio (AER) is a recently developed estimand for non-inferiority active-control prevention trials with a time-to-event outcome. In contrast to the traditional rate ratio or rate difference, the AER is based on the number of events averted by each of the two treatments rather than the observed events. The AER requires an assumption about either the background event rate (the counterfactual placebo incidence) or the counterfactual effectiveness of the control treatment. We develop and present sample size formulae for trials in which the AER is defined as the primary estimand, and draw comparisons with the conventional 95-95 method based on the rate ratio.

Methods

We express sample size in terms of the expected number of events and required

SUBMITTER: Dunn DT 

PROVIDER: S-EPMC12614357 | biostudies-literature | 2026 Feb

REPOSITORIES: biostudies-literature