Topic summary

Immortal time bias in a claims-database study

Evidence › Study critique risk of bias observational data disputed confounding Closed

This is a generated summary. It shows the 5 most-liked posts from a topic of 35, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

mi.almeidaTL2 Moderator14 Jul 2025#1

Immortal time bias in a claims-database study — setting out what I have, and where I think it stops being reliable.

I have seen FLOW (N Engl J Med, 2024) cited in support of a claim I do not think it supports, twice this month, so I would like to work through what it actually shows.

My reading is that the trial is sound for its own question and is being stretched to answer a different one. I might be wrong about that, which is why this is a topic rather than a correction.

What I would like from this discussion: someone who disagrees with me to say why, with the section of the paper they are relying on.

54 likes 12mo

f.wojcikTL2 Moderator1 Aug 2025#11

l.trevino, post #9: Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing. The correction was fair and I had been repeating something I had not checked carefully enough. Go to post

Picking up post #8: that is the part I would want checked first.

Choosing the worst interpretation: "The confidence interval includes a harmful effect" is true if the CI goes from -1 to +5. But assuming the worst-case scenario is not how you use the evidence. The point estimate and the precision both matter.

27 likes in reply to #9 12mo

k.karlsenTL2 Moderator21 Aug 2025#26

mi.almeida, post #1: Immortal time bias in a claims-database study — setting out what I have, and where I think it stops being reliable. I have seen FLOW ( N Engl J Med , 2024) cited in support of a claim I do not think it supports, twice this month, so I would like to work through what it actually shows. My reading is that the trial is sound for its own… Go to post

This follows post #23 rather than contradicting it.

Criticise the method, not the author: a paper with a weak design is not a bad paper by someone with bad intentions. It is a paper that answers a limited question. Sometimes that is what the sponsor wanted, sometimes the researchers did the best they could with constraints.

28 likes in reply to #1 11mo

FFaulknerTL3Regular24 Aug 2025#29

e.okafor, post #10: Picking up post #7: that is the part I would want checked first. Criticise the method, not the author: a paper with a weak design is not a bad paper by someone with bad intentions. It is a paper that answers a limited question. Sometimes that is what the sponsor wanted, sometimes the researchers did the best they could with constraints. Go to post

Coming back to post #27, because the follow-up matters more than the original answer.

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

22 likes in reply to #10 11mo

e.adeyemiTL2 Moderator30 Aug 2025#34

m.dalgaard, post #31: Multiple comparisons: if a paper reports many outcomes, the chance of a spurious association by random chance is real. Pre-specification of primary outcomes matters and secondary analyses are weaker evidence. Go to post

I read post #32 twice before replying, because I had assumed the opposite.

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

30 likes in reply to #31 11mo

Read the full topic (35 posts)

This topic was referenced in

Critiquing an observational claim about a class effect — one year onEvidence › Study critique · 9 replies

This topic was closed 45 days after the last reply. Closing is automatic for quiet topics so that a settled answer does not collect new questions underneath it. If you have a follow-up, open a new topic and link back to this one — that keeps both readable and gives your question its own title.

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