Aggregate verification data across the directory, with caveats

On the subject in the title: Aggregate verification data across the directory, with caveats Working notes rather than a conclusion.

I have spent a fortnight trying to pin aggregate verification data down and I want to set out where I have got to, because I suspect the honest answer is duller than the thread this will produce.

What I have: a consistent observation across a small number of cases, collected the same way each time. What I do not have: any controlled comparison, or any reason to think my cases are representative.

The specific question is whether the pattern survives once the obvious confounder is removed. I cannot remove it with what I have.

Service differences on vendor pages: Janoshik and Medutest results are measurements on vials. PeptideMeter verification records are assessments maintained over time. VendorInvestigate reviews are documentation assessments. We cite all four because they answer different questions.

I would not lead a decision with this, but I would not ignore it either.

Post #2 answers the question as asked. The question underneath it is different.

What I want from this aggregate verification data thread is the list of things that would need to be true for the claim to hold. If we can write that list, we can check it.

Noted, and thank you for writing it out rather than summarising it.

Following this. I have the same question and no better information than the first post.

I read post #3 twice before replying, because I had assumed the opposite.

Repeat determination on the same product line months apart is the measurement that speaks to consistency, and consistency is what most buyers actually want.

The lot identifier has to match across vial, certificate and invoice for any of this to mean anything. It is the floor and it is worth checking every time.

Two sources, same conclusion, and I could not rule out that one copied the other.

Nothing in a verification record is a guarantee about the vial in your hand. That check is yours and nobody can do it for you.

It cost nothing to check and would have cost something not to.

Picking up post #6: that is the part I would want checked first.

The record shows what was measured. Everything beyond that is inference and this site tries to keep the line visible.

Same experience here, different supplier, so it is at least not unique to one of them.

On post #7 — agreed on the reasoning, with one qualification.

Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the conclusion. Testing with the same service verifies reproducibility but uses the same method.

I am reporting what happened, not recommending it.

Post #11 answers the question as asked. The question underneath it is different.

I have no financial interest in anything named in this thread and I want to say so before I comment on aggregate verification data, because it is the sort of subject where it matters.

Interpreting a result: a purity figure is one measurement on one vial on one day. Agreement across two services is much stronger. A single high number does not establish a pattern.

Adding a note of thanks rather than an opinion. I did not know most of that.