Wednesday, June 13, 2018
Wisdom Wednesday: PSA Versus Free PSA
Prostate-specific antigen (PSA) is a protein made mainly in the prostate. A bit of PSA is released into the bloodstream during each ejaculation, and PSA in ejaculate makes it easier for the semen to carry sperm to the fallopian tubes during conception. PSA can have two basic states. It may be bound to another protein or float free.
The total PSA and free PSA tests both measure levels of PSA in the blood. Results help doctors to diagnose issues like prostate cancer and inflammation of the prostate. A total PSA measures all the PSA, including the antigens that are bound and those that are floating freely. A free PSA test only measures the amount of PSA that is floating freely in the bloodstream without being bound to a different protein.
Both tests are used to diagnose prostate issues. A person may have an increased risk of prostate cancer when they have higher levels of total PSA and lower levels of free PSA.
A free PSA test is typically given after a total PSA test to help doctors rule out cancer or to indicate how far cancer has progressed after treatment. The free PSA test is often used before a biopsy to provide initial confirmation of a doctor’s diagnosis.
There are some drawbacks to using PSA testing. There may be high rates of false positives, normal results do not rule out prostate cancer, and people may also have elevated levels of PSA without having cancer.
Because of this, PSA tests are often just one part of a complete diagnosis. If results are at all unclear, many doctors still recommend a biopsy or additional testing to help with diagnoses.
Total PSA ranges may vary slightly:
Age 49 or younger: 0.0-2.5 ng/mL
Age 50-59: 0.0-3.5 ng/mL
Age 60-69: 0.0-4.5 ng/mL
Age 70 or older: 0.0-6.5 ng/mL
When total PSA levels are higher than the appropriate range, a person has an increased risk for prostate cancer. It does not show conclusively that a person has cancer. Doctors will then compare the total PSA with the results of a free PSA test.
A high total PSA level and a low free PSA level generally indicate a risk for prostate cancer. When the ratio of free to total PSA is between 0 and 10 percent, the risk of having cancer may be as high as 56%. When this ratio is greater than 25%, the risk reduces to 8%.
PSA levels normally rise with age so doctors also look a PSA kinetics which reflect how levels change over time. They look at PSA velocity (how rapidly levels are rising) and doubling time.
There have been recommendations by some medical groups to discontinue the PSA as it is often used as an excuse by urologists to perform unnecessary prostate biopsies, a very lucrative procedure. However, the addition of the free PSA when the total PSA is elevated is an excellent alternative or intermediate test in lieu of biopsy.
The total PSA can be elevated from benign prostate hypertrophy, medications to treat an enlarged prostate, repeated pressure on the prostate (bike, motorcycle or horseback riding), rectal exam, ejaculation, UTI and anal sex. I had a patient whose total PSA dramatically elevated from a Brown Recluse Spider bite.
The Bottom Line:
The total PSA is a valuable test for aging men. I recommend it be performed every two years as long as it remains well within the medical norms. If the total PSA elevates, the past tests will provide velocity and doubling time and the free PSA can be performed as well.
Source: May 31, 2018 National Institutes of Health