A preprint whose numbers changed substantially at publication — what changed since

On the subject in the title: A preprint whose numbers changed substantially at publication — what changed since Working notes rather than a conclusion.

Session topic: STEP 2 (Lancet, 2021). Please read it before posting; the discussion is much better when everyone has.

The question I would like us to start with is what the trial set out to estimate, rather than what it found. Once that is on the table we can talk about whether the design could have answered it, and only then about the numbers.

Specific things I would like covered: the population and how far it generalises, how discontinuation was handled, whether the comparator was a fair one, and what the absolute rather than relative effect looks like.

I will summarise at the end and the summary will feed the relevant digest page.

Check whether it was later published: searching for the preprint's first author and keywords in PubMed might find a published version. The published version is the stronger citation if it exists.

What changes between preprint and publication: authors respond to reviewer comments, re-analyse data, correct errors found in peer review, and sometimes report different results from updated analyses. The published version is not the same as the preprint.

On post #3 — agreed on the reasoning, with one qualification.

Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.

Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up.

Server repositories: medRxiv for medicine, bioRxiv for biology. Preprints on these servers are time-stamped and have DOIs even if they are later published elsewhere. Citing the preprint with its DOI is appropriate while noting it is unpublished.

post #6 is right about the mechanism and I think understates the practical bit.

Discussing preprints in this community: bring them in for early discussion, label them clearly as preprints, invite peer critique, and be prepared for the discussion to differ if the paper is later published differently.

Worth separating two things that post #4 runs together.

Unrefereed work is not worthless. A great deal of it survives review substantially unchanged. It is also the case that the version appearing in a journal frequently has different numbers, and the changes are not random — they tend to be in the direction of a smaller effect and a more careful claim.