Which analysis includes all randomized participants, preserving randomization?

• A. Per-protocol includes all randomized participants; ITT includes only adherent.
• B. ITT includes all randomized participants, preserving randomization; Per-protocol includes only those who adhered.
• C. Per-protocol includes all participants; ITT excludes non-adherence.
• D. ITT excludes those who deviated; Per-protocol preserves randomization.

Answer: (B)

This question tests understanding of intention-to-treat versus per-protocol analyses in randomized trials. Intention-to-treat includes every participant as randomized, regardless of adherence or deviations from the protocol, and analyzes them in their originally assigned groups. This preserves the benefits of randomization, keeping the groups comparable and reducing bias that can occur when participants are excluded or reclassified based on what actually happened. It also mirrors real-world effectiveness, where not everyone follows the protocol exactly. Per-protocol analysis includes only those who adhered to the protocol, excluding those who deviated or dropped out, which can distort the treatment effect because the adherent group may differ in important ways from non-adherents and the original randomization is not preserved. Therefore, the analysis that includes all randomized participants and preserves randomization is the intention-to-treat approach; the analysis that includes only adherent participants is per-protocol.