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?
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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.
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.
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.
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.
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.
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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.
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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.
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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