NurseKim_ATL said:

It is worth asking what the claim would look like if it were false.

Adding the part of the answer the thread has not reached. Whatever the answer turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, and invite the correction. That is slower than asserting, and it is the only version that survives being wrong.

The figures, for anyone assembling their own picture. Worth stating the units and the reference range whenever you post a number here. A large fraction of the apparent disagreement in these threads is two people using different units and both being right.

One thing that is still open after NurseKim_ATL’s answer:

What would you measure differently if you were starting again?

VendorMark said:

Worth stating the units and the reference range whenever you post a number here.

I read this differently from VendorMark, on substance rather than tone. Not convinced. The evidence being cited is consistent with the conclusion and also consistent with two other conclusions nobody has ruled out.

Closing the loop on my own question.

Update, and it is the boring outcome: nothing was wrong. The measurement I was reading had moved less than its own week-to-week variation, which somebody said upthread and I did not believe.