Who knows the difference between "after prostatectomy PSA" and "total PSA" ? Is the difference only in precision (an extra decimal place) or are they really different tests?
My husband usually gets test results from Quest laboratory as "after prostatectomy PSA". Last time, for some reason, he got "total PSA = 2.0". Our nurse called Quest and asked for a retest on the same blood sample. We received the result "after prostatectomy PSA = 2.59".
We don't know which of the two PSA values my husband actually had.
Thank you for your help!
Written by
irakor
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It didn't occur to me that a more accurate method could give an extra 25%. But you are probably right, this is the only explanation for such strange test results. Thank you!
There are a few ways to measure PSA.If the expected PSA is 0.1 ng/ml or greater then typically a lower resolution method is used. It is usually cheaper than a higher sensitivity test.
If the expected PSA is lower then an "ultrasensitive" or "post-prostatectomy" test is often used. Sometimes they will have lower thresholds of 0.02 or 0.01 ng/ml.
To answer your question: both are valid and they are generally different tests. To get an idea of what your PSA is doing, it is usually recommended to go with one type of test. Preferably at the same lab using the same methodology.
To complicate things PSA fluctuates. If it is higher or lower for one measurement, most MOs will let a couple of weeks go by and then retest. To complicate things even more, PSA is not really prostate-specific. A small amount is made by other tissues. And to complicate the complication, PSA is a marker but is not always completely indicative of cancer action. Usually, it's a good proxy but not always.
My MO told me that I won't qualify for the PSMA scan because my insurance would disallow it since my PSA is less than 0.3. I'm going to talk to her again because I can show labs with much higher PSA values (as well as labs with undetectable PSA measurements).
FYI My PSA was below .3 but doubling over 2 successive tests over 3 months. Oxford Liberty initially denied me the PSMA but then granted it after my MO did a peer-to-peer conference with their expert.
It's just the way Qwest and other online labs market their PSA tests... the normal PSA test, "total PSA" measures down to one tenth of a unit (0.1), and the "after prostectomy test" measures down to one hundredth of a unit (0.01 or so depending on the assay). So they probably did the first test using the normal PSA assay, and the second one using the ultra-PSA test ("after prostectomy test"), which gave the result to two digits to the right of the decimal.
Exactly, but the results differ: "total PSA" was 2.0 and "post prostatectomy PSA" was 2.59. The two tests used the same blood sample. Probably, the second one is more accurate and we should trust the value 2.59.
The difference is likely due to different machines/assays, because one was the standard test and the other was the uPSA. For example, Beckman-Coulter results are about 20% higher than those returned by Siemens method. This highlights the need to use the same lab/assay/test if trying to establish a trend, as well as keeping other factors constant like time of day and no physical exercise before the test. The results may show which machine/assay was used.
The less sensitive PSA tests that report down to 0.1 are less expensive, were the first test developed back in the 1980s, and still widely used.
The newer ultrasensitive test cost more and report to a lower level. This lower level varies widely based on where you go for the test.
Labcorp ultrasensitive tests report measure to 0.006 at this time. They have varied in what they report over the past say 3 years but have returned to 0.006. When I say report that's what I mean. As they may have always been measuring to say 0.006 but only reported to a higher level. This caused a lot of confusion.
Quest uses a different method "Assay" to measure PSA altogether and it reports I forget either a higher level or a lower level PSA. Meaning if you went to Quest you'd get a different value than if you went pretty much anywhere else. For example (2.2 vs 2.7 against the same blood sample) They can't be compared to other labs taken elsewhere. I don't use Quest because of that. I go to LabCorp because their numbers mesh with labs used elsewhere.
Now even when you go to Labcorp you have to request the standard cheaper PSA Test or one of their two more expensive ultrasensitive tests. They default to the cheaper, standard, less sensitive test of 0.1.
There are two Labcorp ultrasensitive tests they both measure and report to 0.006 but one gives you pretty graphs and they charge you even more for the graphs.
The personnel at Labcorp aren't very knowledgeable about ultrasensitive tests, they have to put a different test request number on your blood sample and say 30 % of the time will run the cheaper test when you want the ultrasensitive ones.
After you get your results You may find they ran the incorrect PSA Test based on your or your doctor's wishes. You can request they rerun your sample with the correct PSA Test and get credit for the wrong test. This is likely what your doctor requested Quest do for you.
My last psa test at labCorp was <.1 , down from 0.8 after adding Xtandi to my estradiol patches which I have been using for 3 1/4 years. I was told way back when that <.1 was “undetectable “.
Yes a < sign indicates the PSA was less than the sensitivity of the test.
Since yours came back <0.1 you can be satisfied with that or begin requesting ultrasensitive tests to follow lower.
So usually no new treatment is initiated when your PSA is below 0.1.
The more sensitive tests let you know things sooner and in the case of immediately after RP can let you know how likely you are to have a recurrence down the line. For example 0.03 six weeks after RP means you're likly to have a recurrence, 0.02 means your unlikely to have recurrence. So ultrasensitive is very important for those tests.
I like to know how low my NADAR was, that's just me.
"Undetectable" is a misnomer, dating back to the days when the test only went to 0.1. The ability to detect to much lower levels exists today. New terminology is needed and the debate is starting as how we should name various levels.
Some may say your PSA is Zero. But if they are looking at the .0 then there may well be 0.099 or 0.065 you get the idea, it's not really zero unless you can read to 0.000 at this time.
I equate this to saying. Both 60mph and 100mph are faster than a horse, If your satisfied with knowing the race car is going faster than a horse, fine. If you'd really want to know if it's 60, 70, 80, 200 mph then you need a better measuring device. Those better measuring devices are Ultrasensitive PSA test for PSA.
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