SURPASS — 11 things I got wrong before I got it right
SURPASS — 11 things I got wrong before I got it right. It is the sort of thing everyone half-believes and nobody writes down.
A confidence interval is the range of effects compatible with the data. Two trials with overlapping intervals have not disagreed, whatever their point estimates look like next to each other.
Cardiovascular outcome trials are powered for events, not for weight, and are typically run in a different population with different inclusion criteria. Reading a weight number out of one is reading a secondary endpoint.
Open-label extensions lose their randomisation. Anybody still enrolled at week 104 is a selected group and the numbers describe that group.
Please do not ask me what dose you should be on. I genuinely do not know and neither does anyone else here.
best — the order this archive was captured in
The registered protocol is public. Comparing the registered primary endpoint with the reported one is a two-minute check and it is how outcome switching gets caught.
Discontinuation rates are a tolerability result. A trial with a strong efficacy number and heavy discontinuation is telling you two things and people only quote one.
the confidence interval is the finding, the point estimate is the headline
Read a press release and the publication three months apart. The hedging in the second one was substantial.
Quoted a figure here confidently, got asked whether it was ITT, went and checked, and it was not. Learned something.
That is the 68-week readout, not the 72-week one. Different trial, different duration.
intention to treat versus completers changes the number substantially
Careful with that mean. The distribution around it was wide enough that it describes very few individual participants.
Right — trial participants get structured support. Comparing yourself to a trial mean is comparing across two different interventions.
phase 2 finds a dose, phase 3 measures the effect
Do you have the publication or the press release?
Small fix — that was the cardiovascular outcomes trial, so weight was a secondary endpoint and the population was different.
Relative risk reduction without the baseline rate is uninterpretable. A large relative reduction on a small absolute risk is a small absolute benefit.
Correction: SURMOUNT is the obesity programme and SURPASS is the diabetes one. The figure you quoted belongs to the other one.
Intention-to-treat analyses everybody randomised regardless of what they did afterwards. Completer analyses only those who finished. The second is systematically more flattering and both are legitimate if labelled.
How long was the randomised phase before any extension?
Started keeping the trial identifiers straight in a note file because I kept mixing up two programmes in the same sentence.
Is that intention-to-treat or completers?
a mean is not a promise
a mean is not a promise
Agreed. And the interval, not the point estimate, is what the trial actually established.
Agreed.
Disagreeing with this line: that is a relative reduction and the absolute numbers are considerably less dramatic.
- 1intention to treat versus completers changes the number substantially9 comments in this branch · started by u/cesar_ivaturi