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PSA Different Standards

Posts: 1
Joined: May 2018

Good Evening Gentlemen,

I'm 61, non-tobacco user, non-drinker, retired military (had exams every 3-4 years), PSA levels always below 2.4, diagnosed with BPH about 4 years ago and no family history of prostate cancer. In March 2018, I had my annual exam with my urologist. Results were tPSA 7.9, fPSA 2.3, %PSA 29. He put me on antibotics for 10 days and follow-up results were 4.6, 1.1, 24%. I had a biopsy and 1 of 12 cores was cancerous with Gleason score of 6.

I read many articles, plus this forum, and decided to go on AS. Follow-up PSA test results (tPSA only) Jul - 2.3, Aug 1.7, Nov 2.0. In Feb 2019, he ordered tPSA, fPSA, %PSA and results were 7.5, 2.4, 32%. After a little investigation, I found out the <4 results used the WHO PSA standard, and >4 results used the Equimolar PSA standard. I used the same Quest Diagnostics clinic for all tests. However, when the order includes tPSA, fPSA, & %PSA, the specimans are sent to a different lab in a different city.

It boggles my mind to think Quest would use two different standards. Last year, if my urologist had not ordered the tPSA, fPSA, & %PSA, I would not have had a biopsy, hence I would not know that I have prostate cancer. I thank the Lord that I found out now, and not later.

I have an appointment with my urologist on Thursday, and this will certainly be a topic of discussion. 

My thanks to all those who have shared their experiences on this forum.


VascodaGama's picture
Posts: 3371
Joined: Nov 2010


Thanks for sharing your experience and the finding on the different PSA standards.

This theme regarding the results of PSA tests has been known by many in this forum not as a difference in standards but as a difference in assays. In fact this has becomed a bigger problem since WHO stepped in the controversy (in 1999) by trying to regulate the assays’ manufacturers’ output values. The truth is that the WHO standards depended on the assays capabilities and methods (CLIA) which differ among themselves and between suppliers.  Assays following the same WHO standards provide different results. For that reason, some manufacturers decided to keep their output reference values that are proper for comparison in-house leading to the chaotic experience as that of yours. It recalls me the times when the videotape format war was rampant between Betamax and VHS. We the consumers needed both VCR if wanted to watch that particular video. VCR manufacturers would not agree in standing by the other’s format. This war ended when the digital-era started with the CDs. These facts regarding the PSA will also end one day when genomics are perfected and replace the PSA as a diagnostic tool in PCa affairs

To those controlling their PCa cases via the PSA (my case also), the best for the moment is to keep testing at the same reliable laboratory. These clinics know well on the facts in differences and usually keep the same assays for the particular tests. Your doctor should know about this. He is the one in fault for testing the PSA in different labs.

Here is an abstract on the differences in assays. The results are wider if one gets tested in super sensitive assays of three decimals digits (0.XXX ng/ml).


In any case, your AS treatment will use other means to judge any progress. One positive core Gleason score 6 is for low aggressivity. How about getting added information regarding the genomics of the cells? This may be helpful in the future when gene treatment becomes common in PCa matters. The 68Ga PSMA PET/CT is also replacing the common CT or MRI in the diagnostic processes. You could also aim in getting one of these exams.

Best wishes.



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