What must investigators ensure when participants end their involvement in a clinical trial?

• A. Notify the sponsor immediately.
• B. Continue collecting data indefinitely.
• C. Ensure proper procedures are followed for participants ending their involvement.
• D. Terminate all trial activities immediately.

Answer: (C)

When participants end their involvement, the priority is to protect their safety and rights while preserving the integrity of the trial data. Investigators must ensure that proper end-of-participation procedures are followed. This includes informing the participant about what withdrawal means, documenting the reason for withdrawal, and conducting any necessary safety follow-up to check for ongoing or delayed adverse effects. They should also manage the investigational product and treatment records according to the protocol and sponsor instructions (for example, return, destruction, or accountability of remaining drug), and complete essential data collection up to the point of withdrawal as required by the study protocol, while respecting the participant’s privacy and consent. If applicable, arrangements should be made for medical care related to withdrawal and timely reporting of safety information to the sponsor and oversight bodies.

Other options don’t fit because simply notifying the sponsor immediately isn’t the universal, required action for every withdrawal, continuing data collection indefinitely ignores the participant’s decision and consent, and terminating all trial activities is inappropriate when only one participant is ending involvement.