Under what circumstances might multiple primary variables be appropriate?

• A. They are never recommended due to regulatory risk.
• B. They should be avoided unless absolutely necessary.
• C. May be desirable, each sufficient to cover the range of effects.
• D. They require separate trials for each primary variable.

Answer: (C)

Multiple primary variables may be appropriate when the treatment is expected to yield meaningful effects across different aspects of the disease, so each endpoint can capture a distinct dimension of benefit. Including several primary endpoints can be desirable because together they cover the range of potential effects the therapy might have. However, this must be planned in advance with a multiplicity-control strategy (such as an adjusted significance level or a hierarchical testing plan) to limit false positives. It’s not required to run separate trials for each endpoint, and regulatory acceptability depends on a clear rationale and prespecified analysis plan.