A comparison of home results against a laboratory result on the same vial — does this still hold?

A comparison of home results against a laboratory result on the same vial — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below.

Comparison of home results against: setting out the arithmetic in full, because I have had to do it twice and I would rather nobody else did.

Every step is shown. If the answer is wrong the error will be visible, which is the point of writing it out rather than posting the result.

Where a home observation and an independent result disagree, the independent one is measuring something more specific. That does not make the home observation useless — it makes it a different measurement.

The disagreement above is smaller than it looks once the terms are fixed.

What you can use home tests for: confirmation that a solution contains peptide (as opposed to being saline alone), rough screening for very different compounds (semaglutide versus totally unrelated compound). What you cannot use them for: precise purity assessment or verification that the identity is correct.

Nothing above should be read as advice about what anyone else should do.

Precision of home tests: most consumer-accessible devices are not precise to the level people want ("is this 99% pure or 97% pure"). They give a yes/no or a rough category, not a quantitative number.

That much is documented. The rest is how I have interpreted it.

The right question for any home test is: what physical quantity does it measure, and what would have to be true for that quantity to answer your question? Most disappointment comes from skipping it.

Where I would look next, rather than where I would stop.

Understood. Thank you for being specific about the limits of it.