Which description best captures the concept of equipoise in clinical trials?

• A. The ethics committee decides which arm.
• B. Participants can choose their own arm.
• C. There is certainty about which arm is better.
• D. Genuine uncertainty about which arm of a clinical trial will provide the most benefits or harms.

Answer: (D)

Equipoise means there is genuine uncertainty within the medical community about which treatment arm will yield the most benefit or the least harm. This uncertainty is what ethically justifies randomly assigning participants to different arms, because no one knows which option is superior and the trial aims to discover the better approach. If there were a clear, established better arm, it would be unethical to randomize or to withhold that treatment. Similarly, letting participants choose their arm or having an ethics committee decide the arm would undermine the unbiased comparison at the heart of the trial. Therefore, the description that there is genuine uncertainty about which arm will provide the most benefits or harms best captures equipoise.