Date and/or Time of First Challenge Agent Administration

**Semantic type:** Temporal Concept

**Definition:** The start date or date and time of the first exposure to any protocol-specified challenge agent that induces the disease or condition that the investigational treatment is intended to cure, mitigate, treat, or prevent, represented in a standardized character format.

**Synonyms:** - Date/Time of First Challenge Agent Admin - RFCSTDTC - RFCSTDTC