Journal club: indirect comparison between two programmes, defended and attacked posts 61–90
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Indirect comparison would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.
Post #62 describes the usual case. This is about the unusual one.
Where the indirect comparison reasoning breaks down for me is the step from the group result to the individual case. That step is almost never argued for.
Adding the measurement that post #62 says would settle it.
The most common failure mode is spending fifty minutes on the effect size and ten on the population. Reversing that ratio would improve most sessions.
Distinguishing three things in the indirect comparison discussion that keep getting used interchangeably: the observation, the proposed mechanism, and the recommendation that gets attached to both.
Post #65 is right about the mechanism and I think understates the practical bit.
Critical appraisal template: (1) What did the trial set out to estimate? (2) Could the design answer that question? (3) Was the population sufficiently similar to your population to apply the results? (4) What was the absolute effect, not just the relative one? (5) What are the two strongest criticisms available?
The strongest argument against my own position on indirect comparison, stated as well as I can state it, since nobody else has yet.
I read post #65 twice before replying, because I had assumed the opposite.
A request rather than an answer: could whoever has the primary source for indirect comparison post it? I have seen the claim three times this month and each version had lost a qualifier.
Reading order that works for these sessions: registry entry, methods, baseline table, primary result, then abstract last. Reading the abstract first anchors everything that follows.
Adding it because I spent an afternoon working it out and nobody should have to twice.
An hour is enough for one paper read properly and not enough for two read partly. The temptation is always to add the second.
For what it is worth, the same held on the two occasions I checked.
Adding a small correction to the indirect comparison summary above rather than a disagreement with it. The substance holds; one of the figures is out by a factor that matters.
Posting my indirect comparison numbers with the method attached so they can be discounted properly. Uncontrolled, unblinded, and collected by someone who wanted a particular answer.
Reading order that works for these sessions: registry entry, methods, baseline table, primary result, then abstract last. Reading the abstract first anchors everything that follows.
I would hold that lightly until someone with a larger sample weighs in.
Confirming post #76 from a second method, which matters more than confirming it from a second person.
The most common failure mode is spending fifty minutes on the effect size and ten on the population. Reversing that ratio would improve most sessions.
I had written a reply contradicting post #78 and deleted it. Here is what survived.
Indirect comparison: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.
One more thing on indirect comparison that took me far too long to see: the two figures people quote are not measuring the same quantity. Once you notice that, the apparent contradiction disappears.
Collapsed as off-topic by two members at trust level 3 or above
STEP 1 (N Engl J Med 2021): The pivotal obesity trial for semaglutide and the reference point for most subsequent comparison. Mean weight reduction was substantially larger than anything previously achieved pharmacologically.
That is the version I use. It may not be the version that is correct.
Narrowing post #84, because the general version has more than one answer.
The figures usually contain the finding and the text usually contains the interpretation. Separating them for the first twenty minutes is a discipline worth keeping.
What I can speak to on indirect comparison is narrow, so I will keep it narrow rather than generalising from it. Beyond that boundary I do not know.
Critical appraisal template: (1) What did the trial set out to estimate? (2) Could the design answer that question? (3) Was the population sufficiently similar to your population to apply the results? (4) What was the absolute effect, not just the relative one? (5) What are the two strongest criticisms available?
Collapsed as off-topic by two members at trust level 3 or above
Two people in this thread mean different things by indirect comparison and are disagreeing about the definition while believing they are disagreeing about the facts. Worth pausing to define it.