If a participant stops treatment or withdraws, what is the investigator's duty?

• A. The investigator should discontinue data collection and remove the participant from the dataset.
• B. The investigator should report the withdrawal to the sponsor immediately.
• C. The investigator should follow the protocol and/or other protocol-related documents to avoid loss of already collected data and ensure trial results are reliable.
• D. The investigator may ignore the withdrawal and continue as if nothing happened.

Answer: (C)

When a participant stops treatment or withdraws, the investigator’s duty is to follow the protocol and any related documents that govern how withdrawals are handled. The reason this matters is to protect the integrity of the trial and the safety of participants. The protocol specifies what data can be collected after withdrawal, what data must be retained from before withdrawal, and how this information will be analyzed. Adhering to these procedures helps ensure that already collected data are not discarded and that the trial results remain reliable and unbiased. The investigator should document the withdrawal (including date and any reason given), continue safety monitoring as allowed by the protocol, and report according to the protocol’s requirements. Ignoring the withdrawal or discarding data would compromise trial integrity, while simply stopping all data collection would undermine the study’s validity.