Second pass at: Fasting versus non-fasting and which tests care

On the subject in the title: Second pass at: Fasting versus non-fasting and which tests care Working notes rather than a conclusion.

Posting a small dataset on Fasting versus non-fasting. It is mine, it is uncontrolled, and the method is stated so it can be discounted appropriately.

What I would like is not agreement but a second dataset collected by someone with no stake in mine. If one exists I would rather read it than argue for this one.

The opening post put the caveat in the right place and I want to underline it.

Time of day: some biomarkers vary across the day. Cortisol in the morning differs from cortisol in the evening. Comparing results from different times of day is comparing things that are not the same.

I would put moderate confidence on the mainstream reading of Fasting versus non-fasting and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.

That reframing is the whole thing. The facts I already had.

Adding the boring version of Fasting versus non-fasting, because the interesting version keeps getting posted and the boring one is usually right.

Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does.

Post #5 and I disagree about the size of the effect, not about the direction.

A trend needs at least three points to be a trend. Two points are a line and a line through noise is still a line.

General information rather than advice about anyone's care. A single value outside a reference interval, on a single draw, in an otherwise unremarkable panel, is usually uninformative.

That is a description of practice, not a recommendation of it.

Worth separating Fasting versus non-fasting as a question about the compound from Fasting versus non-fasting as a question about the documentation. They get answered by different people and only one of them is answerable here.

For anyone finding this later: the short answer on Fasting versus non-fasting is that it depends on one thing, and the rest of the thread is people identifying which thing.

Fasting state, time of day, recent exercise and hydration all move several common analytes. Standardising the conditions matters more than the interval between draws.

It is worth stating the boring hypothesis before the interesting one.

Analytical imprecision: any measurement has an error margin. A small difference in consecutive tests is usually measurement noise, not a real change. Knowing the imprecision helps distinguish noise from signal.

The answer changed when I changed how I was measuring, which was informative.

Two things can be true about Fasting versus non-fasting at once: the mechanism is plausible and the evidence for the size of the effect is thin. Most of the argument here is people defending the first against attacks on the second.

I had written a reply contradicting post #11 and deleted it. Here is what survived.

Repeat before acting is standard practice for an isolated abnormal result on most analytes, and it is standard for a reason.

Worth reading the earlier posts in this thread before acting on mine.

Confirming post #11 from a second method, which matters more than confirming it from a second person.

I keep a log for Fasting versus non-fasting specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing and settled it.