Interesting Situation - PSA

Had 6 month draw (LabCorp) on 01/12/23, which was ordered as uPSA as what I am being tracked with; however, somewhere along the line the standard test was performed. The result of this standard test was <0.1 interesting but not useful for tracking data. Therefore, I paid to have the LabCorp uPSA . Just received the results from the test and being reported as 0.009 which isn't what I "expected" but not hitting any buttons at this time. Plan is to get retested in 30 days and press on from there. Just over 3 1/2 years out from SRT/ADT. We shall see.

Regarding the lab mixup, I always remind the tech drawing my blood that it's for an ultrasensitive test. I, too, once had the wrong (<0.1) PSA test done because of a form coding error.

AFAIK, Labcorp's ultrasensitive PSA test is the most sensitive of the mainstream PSA tests widely available. The "undetectable" for it is <0.006. Keeping in mind that there are some (healthy) non-prostatic structures that can produce minute amounts of PSA (Cowper's glands, the urethra, etc.), a result of 0.009 gets an A+ by my lights.

Into the weeds:

When a given PSA test is repeatedly run on the same blood sample, you usually get values with a range. Independent testing of the ROCHE assay used in the Labcorp uPSA found that for a test sample with an exact quantity of PSA equal to 0.01, repeated uPSA testing returned a standard deviation of ±0.001 under ideal lab conditions. If we take the 2 standard deviations usually used (which captures about 98% of all results), we could expect a variability of ±0.002. Of course we don't have the luxury of ideal conditions in daily life. The bottom line, is that if your sample had been immediately retested, IMO it could easily have come back <0.006 (or even +0.009). With this in mind, plus the fact that our body probably fluctuates in these minute amounts of PSA produced from healthy tissue, you have to expect noise/fluctuations in uPSA testing results. In my early days I was worried about these small changes in my uPSA, but what counts is the overall trend, which may take many data points to visualize.

I found it interesting to learn that when you test a solution that contains no PSA at all with the ROCHE PSA assay, you do not get a zero on the analyzers as you would logically expect, but rather some very low value above zero. These values are used to determine what's called the Limit of Blank and is part of the reason that this particular test cannot reliably measure PSA values below 0.006.

To make a long story short:

A PSA of 0.009 is a long, long way below the official threshold of 0.2 that is used to define biochemical recurrence! Studies have shown that regarding prognosis, a post-op nadir of <0.030 is good; a nadir below <0.010 even better. Newbies to the Forum should note that it may take some time after surgery to reach one's PSA nadir.For example, I was being tested every 3 months, and my nadir (0.007 with the Labcorp uPSA test) happened to occur at 9 months post-op.

So... congrats!

Djin

NorCol said...
Djin, LoB, LoD or LoQ can make one's head spin, thanks for the comments. Right now it's "background" noise. As mentioned prior, enjoy all your posts. Respectfully.

OK. I had the impression you were disappointed in the 0.009 result.

Djin