Evidence · Trials

Subgroup analyses: pre-specified versus discovered

Evidence › Trials randomised trial intention to treat surrogate endpoints estimand

j.habermannTL3Regular16 Apr 2026#1

Subgroup analyses: pre-specified versus discovered — setting out what I have, and where I think it stops being reliable.

I would like to disagree carefully with the settled view on subgroup analyses, and I would like to be argued out of it if the disagreement is bad.

The disagreement is about one step, not about the conclusion. If the step holds I withdraw it entirely.

0 likes 3mo

a.eriksenTL214 Jun 2026#2

This follows the opening post rather than contradicting it.

Intent-to-treat versus per-protocol: ITT includes everyone assigned regardless of whether they took the drug. Per-protocol includes only those who completed it as intended. The two can give substantially different results.

That is the practical version. The rigorous version is longer and says the same thing.

22 likes 1mo

IsaksenTL3Regular27 Jul 2026#3

j.habermann, post #1: Subgroup analyses: pre-specified versus discovered — setting out what I have, and where I think it stops being reliable. I would like to disagree carefully with the settled view on subgroup analyses, and I would like to be argued out of it if the disagreement is bad. The disagreement is about one step, not about the conclusion. If the… Go to post

Worth separating two things that the opening post runs together.

Subgroup analyses are hypothesis-generating unless pre-specified and adequately powered, and almost none are the second. The interaction test matters more than the subgroup point estimate.

10 likes in reply to #1 1d

Promoted into the documentation commons. The content of this topic is maintained at SUSTAIN 6 — trial digest, with named maintainers and a review date. The promotion was discussed in doc review. Corrections are best raised against the document, which is the version that gets kept current.

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