What is the appropriate action for an investigator when a subject shows an elevated white blood cell count without clinical symptoms?

When an investigator observes an elevated white blood cell count in a subject without accompanying clinical symptoms, the appropriate action is to report the finding to the sponsor as an unexpected adverse event. This is crucial in clinical research as the safety and well-being of participants are paramount, and even laboratory abnormalities that lack symptoms can be significant.

Reporting elevated laboratory values, such as an unexpected rise in white blood cell count, ensures that the sponsor can assess the safety profile of the study treatment. Such data can be critical for understanding potential reactions and monitoring the overall risk associated with investigational products, even in the absence of immediate symptoms. This proactive communication helps maintain comprehensive safety oversight during the clinical trial and facilitates informed decision-making regarding participant management.

In contrast, hospitalization for transfusion would be inappropriate if the subject does not show clinical symptoms indicating the need for such intervention. Repeating laboratory tests indefinitely could delay necessary actions and is not an effective method for handling unexpected changes in laboratory results. Faxing a handwritten serious adverse event report to the FDA is not typically the procedure for unexpected laboratory findings that do not present a serious clinical condition but would be more relevant if the situation escalated or warranted immediate regulatory reporting.