Specifying a target trial prevents immortal time bias and other self-inflicted injuries in observational analyses

Abstract

Many analyses of observational data are attempts to emulate a target trial. The emulation of the target trial may fail when researchers deviate from simple principles that guide the design and analysis of randomized experiments. We review a framework to describe and prevent biases, including immortal time bias, that result from a failure to align start of follow-up, specification of eligibility, and treatment assignment. We review some analytic approaches to avoid these problems in comparative effectiveness or safety research.

Keywords: Comparative effectiveness research; Immortal time bias; Observational; Selection bias; Target trial; Time zero; studies.