One year Post RP G3 (90%)+ G4 (10%), one .04 mm focal margin.

[Steve507]

Hi! I'm Steve, a 61 year old who is undetectable: three PSA values 0.01 and one 0.02 for a year. I am here to listen, learn, and support.

My question is at very low levels do PSA values fluctuate independent of the lab or assay used?

Steve

[Tall_Allen]

Yes, they can, and should be ignored unless there are three consecutive increases over 0.03, or have reached 0.1.

[Jeff85705 in reply to Tall_Allen]

What if the only lab I can use reports only "less than 0.1 ng/ml"? I understand the seriousness of consistent rises, but isn't 0.0x within the range of error? And can't there be variations between labs or even within a lab?

[Tall_Allen in reply to Jeff85705]

It can vary slightly even from day to day when numbers are that small, so it is the pattern you look for. You can't get an ultrasensitive PSA test in the UK?

[Jeff85705 in reply to Tall_Allen]

I'm in Arizona, not the UK. My Medicare Advantage plan uses only Labcorp.

[RichNJ in reply to Jeff85705]

labcorp.com/tests/140731/pr...

[Magnus1964]

Welcome Steve. This is place to ask questions.

[Steve507 in reply to Magnus1964]

Thanks

[dadzone43]

They can. That is why it is recommended to use the same lab consistently. Any test has some range of variation, and particularly at the extremes of high or low.

[RonnyBaby]

Some labs / tests report more significant digits (0.02 vs 0.002).

I had two tests done within a week of each other and those were the results.

When you are at the extremes of an instruments range(s) you MIGHT lose a 'bit' of accuracy.

For what it is worth, once I used the same lab, the results were consistent (<0.02) when I was undetectable (nadir) for close to a year.

Some claim that there are no errors in the 'accuracy' of these machines - I believe that some minor fluctuations could occur, but a jump of one tenth of a percent would get my attention - unless I was radiated only - my understanding is that radiation nadirs can bounce a bit (no ADT was involved).

The bottom line message ?

Depends on the treatments and the labs and the time elapsed as the patient deals with their particular type of PCa - they are not all the same ....

[Steve507 in reply to RonnyBaby]

Thanks...

have yet to hear of someone who is less than 0.1 level report PSA values droppingl, e.g., 0.03 to 0.02. Probably an anomaly.

[AlanMeyer Moderator]

Here are some reasons that, I think, can cause non-significant variations over time:

1. Measurement resolution. In theory, a reading of 0.01 on a machine that can resolve to 0.01 can mean anything from 0.000 to 0.015. 0.02 can mean 0.015 to 0.025. If your actual PSA was 0.015 (and that means something less precise than 0.0150) it could be reported either way.

2. Variations in the calibration of the machine - due perhaps to how it was calibrated, when it was last cleaned, whether any tiny residues remain in the machine that weren't part of your sample, the temperature of the room or other conditions at the time of testing, and maybe other factors.

3. Variations in the sample. 0.01 nanograms / milliliter is a really, really, really tiny amount. We're talking about one hundredth of a billionth of a gram. If blood draws were made at the same time from both arms, would they both have the same PSA concentration down to 0.01 ng? I don't know if anyone has tested that, but it wouldn't surprise me if blood concentrations vary at least a tiny bit, in different samples of the blood supply.

4. Variations in prostate cell activity. Cells in our body do different things at different times. For men with no cancer and normal PSA, it is not uncommon for the production of PSA to vary a few percent, even up to 30% (according to one doctor I spoke to about this) for reasons that are not yet fully understood. It may have to do with when you last exercised, what you had for breakfast, whether you've been out in the cold, or who knows what.

I think it's reasonable to discount the significance of the variation you've seen in your PSA.

Alan