[PSA] test results are not what most of this community thinks it is
Explainer, as requested in the last thread: test results are not what most of this community thinks it is.
On inter-lab disagreement, which generates more heat here than anything else.
Two services running different gradients, integrating differently, at possibly different wavelengths, will not produce identical numbers on the same material. A point either way is ordinary. Half a point is close agreement.
The productive response to a gap that size is to post both results with both methods and let the log accumulate. The unproductive response is to pick the lower number, call it the truth, and open a dispute. Members have done the first for long enough now that the bands in the vendor tables are genuinely informative.
What a result posted here is actually worth, and how to make yours worth more.
A single figure with no batch identifier is about a vial nobody can locate. Add the batch and it becomes about a lot. Add the claimed figure from the certificate and it becomes a comparison. Add the service and the date and it becomes reproducible. Say that you paid for it yourself and it becomes independent.
Five extra fields, thirty seconds of typing, and the difference between a comment and a row in the log that will still be useful in three years.
Kept every report as a PDF with the batch in the filename. Two years in, it is the most useful folder I own.
If somebody has the same thing measured a different way, post it next to mine and we will see whether they agree.
best — the order this archive was captured in
Inter-lab variance on this assay runs roughly a point either way, driven mostly by gradient and integration. Two results inside that band agree; they do not disagree quietly.
Agreed on quoting the claim alongside the result. Half the arguments here are two people comparing to different reference numbers.
Area percent and net peptide content are different measurements and most reports give one. Quote which, or the comparison downstream is meaningless.
Yes — date of analysis, because a result from two years ago describes a different manufacturing month.
Disagree that this is a discrepancy. 98.8% against a claimed 98.5% is inside ordinary inter-lab variance in either direction.
Correction: that is the claimed figure, and the measured one is the higher of the two in your own screenshot.
The template is vendor, compound, batch, service, claim, result, and who paid. Every one of those fields exists because a result missing it has been argued about here before.
Have now spent more on testing than on some of the orders. No regrets — the log is the reason I can buy without agonising.
A series across separate lots estimates a process. Repeat tests on one lot estimate the measurement. Both are useful and they answer different questions.
Tested three lots over a year rather than three vials from one lot. Cost the same and told me something completely different.
Tested three lots over a year rather than three vials from one lot.
Disagreeing with this line: that gap is ordinary variance, not a contradiction between the lab and the certificate.
Merged with the other thread on the same batch so the results sit together.
CPC BPC, batch matched the paperwork, VendorInvestigate came back 97.4% against a claimed 97.0%. Paid for it myself, posting it because the log is only worth anything if people do.
Split one vial between Medutest and PeptideMeter. The two numbers were within half a point of each other and I stopped worrying about which lab to trust.
Right, and a point or two between services is ordinary. It is agreement, and every month somebody posts it as a scandal.
net peptide content if the report gives it, and say which you are quoting
First result I ever posted here got asked for the batch number and the claim. Fair, and my posts have been better ever since.
That service reports area percent by default. Worth stating, since the thread has been comparing it to a mass figure.
Split one vial between Medutest and PeptideMeter.
lukas_vermeulen is right that the band matters more than the peak. Consistency across lots is the finding.
CPC came back 97.1% on a claimed 97.0%, which is agreement not a discrepancy
Sent a vial in specifically to check a supplier’s claim after a good experience. It matched. Boring result, worth logging.
[removed by moderator]
say whether you paid for it yourself
Is that the same lot as the one in the thread from last month?
date of analysis matters as much as the number
three lots beats three tests on one lot
three lots beats three tests on one lot
This is why the template has a batch field. Without it the result is about a vial nobody can identify.
vendor, compound, batch, service, result — that is the template
inter-lab variance runs a point or two, plan your outrage accordingly
- 1Sent a vial in specifically to check a supplier’s claim after a good…9 comments in this branch · started by u/phase_two_pete
- 2Split one vial between Medutest and PeptideMeter. The two numbers were…7 comments in this branch · started by u/lukas_vermeulen