Expected vs Unexpected Adverse Event

The classification of adverse events as expected or unexpected determines the urgency and nature of regulatory reporting requirements and influences how events are characterized in safety communications. An expected adverse event is one whose nature, severity, specificity, and outcome are consistent with the information contained in the relevant reference document, typically the Investigator's Brochure for investigational products or the approved product labeling for marketed products. An unexpected adverse event deviates from this reference in a clinically meaningful way.