Estimand (ICH E9(R1))
What a definition is not
A definition is SPEQ’s plain-language decode of how a term is used in practice, cited to the documents that define it. It is a practitioner reference, not legal or regulatory advice, it does not replace the definition in the source, and where a regulator’s wording differs the regulator’s wording governs.
A precise description of the treatment effect a clinical trial is designed to estimate, defined by five components: the population, the treatment conditions being compared, the endpoint, how intercurrent events such as treatment discontinuation or rescue medication are handled, and the population-level summary measure. The estimand aligns the trial’s objective, design, and analysis around one clearly stated clinical question.
The estimand framework was introduced because, without it, different implicit choices about handling events like dropout or rescue medication use could quietly change what clinical question a trial was actually answering, even though the stated endpoint looked identical on paper.
Each of the five attributes is chosen deliberately at protocol design stage: the target population, the treatment conditions being compared, the endpoint itself, a pre-specified strategy for each type of intercurrent event, and the summary measure used to express the treatment effect across the population.
The chosen estimand is carried consistently from the protocol into the Statistical Analysis Plan and, ultimately, the Clinical Study Report — it replaces ad hoc, after-the-fact analysis decisions with an explicit statement of the clinical question the trial is designed to answer.
- —Defined by five attributes: population, treatment conditions, endpoint, intercurrent-event strategy, and population-level summary measure.
- —Intercurrent events, such as treatment discontinuation or rescue medication use, must be handled by an explicit, pre-specified strategy.
- —Chosen during protocol development and carried consistently through the Statistical Analysis Plan and Clinical Study Report.
- —Different estimand choices for the same nominal endpoint can answer meaningfully different clinical questions.
ICH E9(R1) Addendum on Estimands and Sensitivity Analysis in Clinical Trials
Frequently asked questions
What is Estimand (ICH E9(R1))?
A precise description of the treatment effect a clinical trial is designed to estimate, defined by five components: the population, the treatment conditions being compared, the endpoint, how intercurrent events such as treatment discontinuation or rescue medication are handled, and the population-level summary measure. The estimand aligns the trial’s objective, design, and analysis around one clearly stated clinical question.
Which regulations cover Estimand (ICH E9(R1))?
ICH E9(R1) Addendum on Estimands and Sensitivity Analysis in Clinical Trials