PURPOSE: Artificial introduction of immortal-time due to study design choices remains one of the most consequential and under-recognized threats to the validity of real-world evidence (RWE) used in market access and health technology assessment (HTA). When eligibility criteria are applied after treatment assignment, or when patients are misclassified into treatment strategies, estimated treatment effects can be biased — with direct implications for reimbursement decisions, comparative effectiveness claims, and external control arm acceptability. This workshop will equip attendees with a structural framework to diagnose design decisions that introduce immortal-time and provide concrete, implementable solutions grounded in the target trial framework. Participants will learn to identify the two principal mechanisms generating immortal time, apply design fixes, and critically appraise RWE submitted in HTA dossiers.
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