Difference in PSA results: Hello: I do... - Advanced Prostate...

Advanced Prostate Cancer

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Difference in PSA results



I do understand there can be a difference in blood test results from lab to lab, but how vast can this difference be?

I have Kaiser for insurance and have always used them for PSA, and all blood work. My last 3 PSA results were April second: 1.18, July second: 0.82, and urologist wanted retest July 30: 0.84: all tests were done 0830 hours each time.

Health Testing Centers was offering free PSA tests so I got one from a local LabCorp near me Oct. 8, done at 0900 hours...the results were 1.4; huge difference!

Is such a LARGE difference from lab to lab normal...I expected a difference, but nothing this large; this seems such a huge jump?

14 Replies

Large discrepancies could be explained by different techniques among different labs.


Most PSA"s are done by automatic reading equipment, such as a Beckman Blood Analyzer.

In the same week one day after the other I am aware, of a friend who had two results back to back being at 9:am----0.3, and <than 0.3--------now this is a big deal, for this friend----one result says it can detect something, and the other says it cannot. In analyzing what happened with this person--what was found the day the individual tested 0.3, he got up had nothing to drink and was dehydrated. The next day this person, had juice and coffee, was fully hydrated and got an undetectable reading of less < than 0.3.

So not only is the time of the day important, but also the amount of normal amounts of water in the blood. Being dehydrated concentrates the blood, and concentrates your cancer cells present. Remember, our tests can only go so far as to accuracy, and cannot detect what is undetectable. And being undetectable does not mean there is nothing there.

But if you get a number that concerns you repeat it, with the same lab, asap--at the same time and with the same amount of fluids.

When I go--my time has always been 9:15 AM + or - 10 minutes. It is always on a Wednesday,and i have 2 glasses of water---total of 16 ounces, 15 minutes, before the blood draw.

If you use different labs, they may have different Analyzers made by different companies.

So always keep everything consistent.


That's why it is best to use the same testing lab to the extent you can.

You mentioned LabCorp in the final PSA test result, suggesting that it might be a different lab than the others. IIRC Labcorp generally uses Beckman-Coulter, while Quest uses Siemens.

The two techniques produce different results. I wrote a post about it. Beckman-Coulter results are about 22% higher than those returned by Siemens method.


That could explain some of the last large change.

As for the others, as Nalakrats points out, there are many variables besides labs and instruments. Most of the variables are in you and difficult to control. Going to the same lab at the same time and trying to maintain consistent hydration is a good start but no guarantee.

My take-away is that the PSA measurement, like all measurements, is imperfect. The results aren't meaningful in the second decimal place. Speaking strictly for myself, any change in a single reading of less than 10%, in either direction, is not really meaningful. The trend over time is more useful.

OldFart81 in reply to FCoffey

Did you reverse the figures?

Here's what Quest noted on my PSA report last week:

"The test result will be approximately 20% lower when compared to the equimolar-standardized total PSA (Beckman Coulter). This test was performed using the Siemens chemilluminescent method. Values from different assay methods cannot be used interchangeably. PSA levels, regardless of value, should not be interpreted as absolute evidence of the presence or absence of disease."

I read that info as saying a Siemens report is roughly 20% HIGHER than Beckman Coulter.

FCoffey in reply to OldFart81

No, I did not reverse the figures. Other way around. Siemens reads 22% lower.

"test result will be approximately 20% lower when compared to the ...(Beckman Coulter)."

OldFart81 in reply to FCoffey

Guess I need coffee

900312611 in reply to FCoffey

I called Labcorp, they said their method used is: Electro-chemiluminescence immunoassay (ECLIA)...I have no idea what method Kaiser uses and from past experience with dealing with them is like talking to a politician...so now I'm trying to search eclia and maybe I can find a percentage difference; in the mean time if any of you know the difference please let me know.

Thank You

FCoffey in reply to 900312611

Roche offers an ECLIA PSA test. It is referenced to the WHO standard, the same as the Siemens test.

Some factors to consider regarding PSA lab reports ... from my experience:

• Jubulation with each PSA coming back (0.00) from each 3 month testing over 4 years (now passing the 7th year). Keeping each PSA Lab Report letter treasured in its own folder.

(Radical prostatectomy, subsequent 3 month Lupron and Prolia over 7 years now. A very painful lesion in a vertebrae, 3 on the liver, one on the adrenal gland, pain in a few bones. Decimating fatigue and depression. “Then why is the PSA (0.00).” Am told ... because the ADT is keeping the cancer cells indolent, hibernating so they are not producing PSA.)

• “Well,” I say to the Urologist and Oncologist, with all smiles! Only to be repeatedly told: There were quite a few “hot-spots” that lit-up on your scans ... to be realistic the prostate cancer will eventually return, and it will kill you. So there was no “Five-Year Survivor Party” from the PSA reports.

• I wanted to relax ... several times even stop the treatment ... the Lupron ... due to the PSA being (0.00), but again and again told that the ADT is keeping the micro-metastatic lessons hibernating, not growing. If we stop treatment (ADT) the cancer cells will take off with two consequences: (1) The cancer cells will wake-up, and grow more aggressively ... with a death more “painful” than those of ADT. (2) Other subsequent treatments for reoccurrence can be as bad or even worse.


My point is that I no longer gloat over the “good” PSA Lab Reports every three months as I did before. My main focus is to control the pain as I am hooked up with Pain Management, curse the cancer, and try to live.

As ADT is now used over longer periods of time now than it was in the past (i.e. Lupron for life) many or some dudes are being diagnosed with many metastatic bone lesions even with a PSA of (0.00) or a normal number.


Don’t sweat over the small peaks and valleys in the PSA results as (1) The cancer cells are still there. And (2) in the testing there is a range above and below what the actual number is.

The night I found out I had prostate ca, the hospital took a blood sample and did a psa at their lab and sent off a sample from the same blood draw to another lab. The Hospital’s PCA result was 352. The one they sent off came back 267 ! Crazy.

There is a range within the numbers ... it’s not like counting the exact number of dimes in your pocket.

Reply to 900312611:

Labs are like kissing two women and only one of them gives you a boner...Stick with the one that gives you a boner...

Good Luck and Good Health.

j-o-h-n Wednesday 10/10/2018 6:07 PM EDT

And a “good” PSA number (or no number 0.00), in some cases gives a false sense of security: Those stray prostate cancer cells (few in numbers) are still alive ... then you’ll be shocked when subsequent scans show up new lesions.

Often we go through treatment, and clinically we have no idea what is actually going on? Generally speaking “there is no cure, it will come back.” (Some reports 10, 15, or 20 years?)

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