How to find out what psa standards are used by different labs for psa testing

Various articles say to make sure to have psa testing at the same lab,
due to 2 different psa testing standards that exist and that a given lab or its equipment might use either standard,

and that the psa
results can vary widely between the 2 standards.
(some articles said even between 2 different machines using the same standard)

And if someone uses a different lab and sees 2 widely different results,
it can be upsetting and challenging to know if its due to the different standards
that might be used or just that psa has gone up or down for other reasons.

But I can't find out what standard is used by the labs I've contacted and its
not mentioned in their online test menu or guide under psa tests. Have made lots of calls and web searches.

Even when I found out the machines used at least at one labs center that does
the testing for my area, could not get thru to anyone at the machine manufacturer
who knew the answer.

psa standards are not the same as the methodology used to do the psa test,
such as ECLIA.


Reason for asking - am changing medical groups so that might need to use
a different lab company to do the testing, and just can't figure out how to find
out that information - the regular customer service lines don't even know what am
talking about. Seems that its important information to know.


Finally, does anyone know if this "different standards used at labs can result indifferent results" applies to other
lab testing, like blood counts or testosterone, or lipids or other common tests we
might need to track ADT or chemo side effects for example ?

To expect psa to be consistently accurate is unrealistic. Just like everything else it varies by a small amount and the trend is the the most important thing to take away.
Psa varies by time of day the test is taken and also by the season of the year. Add to this the variance in labs and machines.
The founder of Yanna took his psa daily for 30 days straight and readings differed by 30%.
Multiple psa readings over time showing a consistent trend are the most reliable.

A few thoughts:

Once you start with a lab stay with it.

If you need to change doctors which is not unusual with this disease , you're better off using an outside lab to avoid switching.

If you have say a Lab Corp branch near you, you can just walk in give them your script (or call for an appointment) and they'll send results to your current doctor. There's no need to have your doctors office do the tests.

Minor variations in results won't dictate different treatments.

I'm convinced though I wasn't once that ultra sensitive test is best particularly if you're in high risk category .

Just my opinion based on moving around the county for treatments.

Bob

To best be comparing apples to apples I figure staying with the same lab for PSA tests makes sense. I do, and also abstain from sex for about the same time before each test. And going in for my quarterly test tomorrow.

If anybody wants to go into overload mode on the topic of variation in chemical testing, Google something called uncertainty in chemical testing.

Pratoman, thank you. Great article.

You can call the lab and ask them.
Quest Labs uses two different machines and methods. If you are testing for PSA and free PSA at the same time, they will use Beckman Coulter - HYbri Immunoassay Method. If you test for PSA alone, they use Siemens Chem Method Bayer, the results vary quite a bit between the two for PSa.

USC uses Chemiluminescent Roche Cobas 600/WHO, UCLA uses Roche Cobas E602, these two results are pretty close.

Also, WHO result is approximately 75% of the Hybri standard (from what I read from one article).

So, like someone said above, the trend is what you are looking for, but comparing different methods and machines may not be as meaningful as comparing same method/machine.

Akai and Gemlin - thanks for the thoughts on looking for the trends - thats what have done until this move to other area and perhaps needing to change labs.

Akai - thats great that you found out that info by calling - I have had very little
luck with that (calling to ask which of the 2 standards used)
I've tried several different departments at labcorp and a large hospital chain in my area, for example.

The labcorp test menu has the name of the method, which seems to be Roche ECLIA for both total and free - but I didn't think that that data was a clue to which psa standard used. Just don't know if the psa standard is something tied to a machine or the reagents and process used to calibrate it and do the testing. so labcorp is still a mystery.


on reading your post about quest - you mention the Siemens Chem method Bayer - does it mean that that one uses the WHO standard ?
(you mentioned for the free psa uses the hybritech std but not the std used for that Siemens Bayer machine, is why I'm asking.



I contacted Siemens last week and they did not know the standard of the machine
(I think Dimension) that the hospital chain said they used for total psa regular (the hospital chain
processing lab did really try to look for data on this question but did not see it.


And as you point out, if different standards are used by the same lab for 2 different
types of psa tests (as you mention for quest) then that adds another layer of complexity in addition to what Halbert mentioned. so one has to be careful to get the same kind of psa test at the same lab.

finally, on that topic, I had done the labcorp regular total psa for a long time,
then got one more lab from previous dr and it was for a reflex total and free
(which meant free part done only if psa between 4-10, which mine was not)
labcorp claimed that the total psa part was exactly the same as the standalone
total psa test I'd had for many years.
Yet the result was not as large as I would have thought it would be based on current psadt trends, alas and now am wondering if indeed its just like you mention at quest,
that the other psa standard was used for that total/free test (and i have no idea which standard labcorp uses for even the regular total one still)

i asked new dr if they would let me take the labcorp 010322 that had taken for a long time, and to let me take it at labcorp instead of their hospital chain - for the
very reason of the 2 psa standards and not knowing which std was used by which lab -
which led to this whole post. I'll know those results in a couple days.

A question about LabCorp's ultrasensitive PSA test:

LabCorp's website says the reference range of their ECLIA test is: "0.000 - 4.000".

But don't we all know that there are no currently-available PSA tests able to measure below 0.001?

My test result was given as 0.009, which I realize is acceptable. But it is not clear to me whether that means, on the one hand: A) "This test is accurate to such low levels that your test detected SPECIFICALLY a value of 0.009" or whether, alternatively, it means: B) "This test can reliably detect down to a level of 0.01. The level of PSA in your sample was undetectable, so the 0.009 result indicates that it was below the lowest level our ECLIA assay can detect."

While 0.009 is encouraging, if it means the latter rather than the former, then that would be very informative. And besides, I will need to be able to place this number in the perspective of the numbers I will be getting in future years.

Thanks for any clarification.

Rodney.

I had to change labs so what I did ( as I will be having SBRT in a month ) was had several tests done several weeks apart to establish a baseline for PSA and Testosterone.