Your "True" PSA may be substantially higher than your reported PSA.
It is critical to use your "True" PSA test level which may be substantially higher than your reported PSA value because of WHO PSA test calibration and/or treatment for prostate enlargement (BPH).
PSA is the prostate-specific antigen blood test used for prostate cancer screening.
Early Warning from Elevated or High PSA
An elevated PSA or a high PSA provide early warning of prostate activity for a smart prostate cancer screening strategy. (Links take you to one of our website pages that opens in a new window.)
"True" PSA May Be Much Higher than Reported PSA
However, your "True" PSA may be higher, and perhaps much higher, than your lab reported PSA value.
For example, you may be surprised to learn that:
Your "Underlying" "True" PSA is the value that your physicians should use to assess your risk with the help of prostate cancer risk calculators or rules of thumb about threshold level of concern, such as 4.0 or 3.0 or an age-adjusted threshold level. For risk assessment, "True" PSA is Hybritech calibrated and adjusted for specific medications to treat prostate enlargement (BPH), as explained below. I discuss your "Underlying" "True" value in my next blog post: Elevated PSA? Is your "Underlying" PSA lower?
Increase WHO Calibrated PSA Values to Hybritech Calibration
There are two common PSA calibrations that give different PSA values for the same blood sample. Hybritech calibration refers to the original PSA test approved by the US FDA.
Beckman-Coulter bought Hybritech. Many PSA tests supplied in the US are Hybritech calibrated, but many others are WHO (World Health Organization) calibrated, which creates the problem.
In order to standardize PSA calibration, the WHO developed a different calibration that is often used in many parts of Europe and some other parts of the world, including the US. Physicians should use Hybritech calibration because it is used by the two most prominent prostate cancer risk calculators and by many studies that were used to develop rules of thumb and PSA threshold levels of concern.
Hybritech calibration increases each WHO PSA test by about 25%. For example, a WHO PSA level of 3.2 is roughly comparable to a Hybritech PSA level of 4.0. See our PSA testing best practices page that opens in a new window. For our examples:
Unfortunately, many lab reports do not identify the calibration of the PSA test value. You may have to ask the lab or your physician for help identifying the calibration of each of your PSA tests. If you can’t determine the calibration with certainty, then you must guess using any clues available.
Adjust PSA Values Upward for Treatment of Prostate Enlargement (BPH)
Many men suffer from prostate enlargement. BPH (Benign Prostatic Hyperplasia) treatment to shrink prostate volume using Proscar (finasteride) or Avodart (dutasteride) can reduce PSA levels by roughly half. Therefore, you and your physicians should follow common practice and double PSA test values during periods of BPH treatment. For our examples:
View this adjustment with caution because your PSA response to BPH treatment may be more or less than average.
Flomax (tamsulosin hydrochloride) treatment does not have this effect.
Increase PSA Values for WHO Calibration and BPH Treatment
"True" PSA is even higher for men treated for prostate enlargement caused by BPH who have WHO calibrated reported PSA values. For our examples:
Estimate Your "True" PSA before Proceeding with Smart Prostate Cancer Screening
The "True" value of your elevated PSA or a high PSA provides early warning of prostate activity for a smart prostate cancer screening strategy. Calibrate your PSA test, if WHO calibration, and adjust it for BPH treatment, if appropriate, before taking any other smart prostate cancer screening steps. I discuss your "Underlying" "True" value in my next blog post: Elevated PSA? Is your "Underlying" PSA lower?
Tom Neville, PhD, is a prostate cancer survivor with a mission to help men make better decisions. He is a Rhodes Scholar from Yale, Phi Beta Kappa, with a Stanford PhD who has worked with leading prostate cancer researchers.