Intention-to-treat analysis is defined as...

• A. Analyzing only patients who adhered to the assigned treatment.
• B. Analyzing outcomes based on the treatment actually received.
• C. All patients entered into the trial are analyzed according to the treatment they were assigned.
• D. Excluding patients who dropped out or deviated from the protocol.

Answer: (C)

Intention-to-treat analysis preserves the randomization by including every participant in the group to which they were originally assigned, regardless of whether they actually received or adhered to the assigned treatment, or even if they dropped out. This approach keeps the treatment groups comparable at baseline and reflects the reality of how a treatment would work in practice, where not everyone follows the plan perfectly. It avoids bias that can arise if people are reclassified based on what they actually did, or if only those who adhered are analyzed, which can distort the true effect of offering the treatment.

If you analyze only those who adhered to the protocol, or assign outcomes based on the treatment actually received, you’re moving away from the randomization that helps balance both known and unknown confounders, which can bias the results. Excluding dropouts or deviations similarly lowers the completeness of the randomized comparison and can skew the estimated effect. So the definition that captures analyzing all randomized participants in their assigned groups best aligns with preserving the integrity of the randomization and providing a real-world estimate of the treatment strategy.