Annual test with a small twist

I was treated with brachytherapy at Princess Margaret Hospital in Toronto eleven years ago. I went back for my annual test this week. The news:

May 2010 psa 5.54
July 2020 9.58
Nov 2010 7.88
Dec 2010 4.35
Mar 2011 4.74
Sep 2011 2.64
Mar 2012 2.41
Dec 2012 3.49
Mar 2013 2.06
Aug 2013 2.20
Nov 2013 1.08
Mar 2014 1.87
May 2014 1.08
Nov 2014 0.93
Jul 2015 0.96
Jan 2016 0.36
Jul 2016 0.40
Mar 2017 0.16
April 2018 0.05
May 2019 0.06
May 2020 < 0.05 “undetectable”
May 2021 0.03

This was an interesting one.

The good news: the last three years 0.06; less than 0.05; 0.03.

The thing I wondered about: why did it say “undetectable” last year and not this year?

My interpretation of what my doctor said was that labelling last year’s result as “undetectable” was a bit of a mistake. There are still some prostate cells remaining, producing a small amount of psa. This change in labelling wasn't because of a new, more sensitive test —same lab, same test. The key thing is the trend. Nothing to worry about. Things are going well. See you next year.

So not quite the 100% total victory last year’s test suggested. But maybe just fine. I guess this is never really over.

If the lab report itself has 2 decimal places (i.e., reads 0.03 and not 0.030) then it cannot have been run with Labcorp's ultrasensitive, which goes down to 0.014 and reports its undetectable as <0.014.

Before my latest Labcorp uPSA result became available on the Labcorp patient portal, my uro had gotten the results and posted it on his practice's patient portal. My previous result had gone up, to 0.037 (from <0.014) and I was eagerly awaiting this result. When I saw the result, 0.02, I immediately thought "rats they ran the wrong test" -- some 2-decimal test -- and while 0.02 is OK as a value, the right-most digit of a lab test is always uncertain. I wrote back "please check if the value from Labcorp is actually 0.020 rather than the 0.02 you posted. In fact, my uro replied the result was indeed 0.020 as I confirmed a few days later at the Labcorp portal. Moral: Labcorp's 3-decimal place test will always have 3 decimal places; however, sometimes a zero can be lost in the translation, um transcription. The final zero doesn't change the result of the test -- it changes the precision of the test.

The < sign in a result isn't anyone's comment or opinion; it simply means that the LDL (lowest detectable level) for the test is the value without the < sign, and your value was something lower, hence the < sign. So you get two pieces of information: what the lowest value is that the test can detect, and the fact that your value was something lower -- untetectable for that test.

An actual result of 0.03 (with 2 decimal places on the original lab report) might have been run with, e.g., Quest's ultrasensitive test, which can detect down to 0.02 if I remember correctly.

For my uro's other patients (who aren't as fussy as I am), they run the PSA test in-office with Labcorp equipment. I remember he told me this test can detect to down to 0.05, with <0.05 as its undetectable.

One assumes a result of 0.03 could represent anything from 0.025 to 0.034; however, if this is indeed a different test than last year's, as it appears, you really aren't comparing apples to apples. A 2-decimal test might return 0.03 and 0.02 or 0.04 if run again on the very same blood sample. You lose a little information going from <0.05 to 0.03, because knowing a value was below 0.05 doesn't tell you whether it was above, the same as, or below 0.03. Your PSA recent values look fine.

IMO men who had radiation as their primary treatment don't need a 3-decimal PSA test, since BCR for them is a whopping 2.0 over their nadir. It's some of us RP guys that like to obsess.

Djin

Looks like a great outcome!