Prostate Specific Antigen (Free) PSA
Understanding Prostate Specific Antigen (Free) PSA
What is Prostate Specific Antigen (Free) PSA?
The Prostate Specific Antigen (Free) PSA test measures the levels of unbound or free prostate-specific antigen (PSA) in blood. It helps in differentiating between prostate cancer and other prostate-related conditions, such as prostate inflammation and an enlarged prostate. This test is often used in conjunction with the total PSA (free and bound PSA) test and other diagnostic tools to assess prostate health.
The prostate is a small walnut-shaped gland located just below the bladder and in front of the rectum in males. It produces a protein called prostate-specific antigen (PSA) that is mainly found in semen (also produced by the prostate gland) and is present in small amounts in the bloodstream of all men. It helps liquify the semen and facilitates sperm motility during ejaculation in males.
The Prostate Specific Antigen (Free) PSA test helps determine the level of free PSA in men. Unlike total PSA, which measures the total amount of PSA in the bloodstream (both free and bound to proteins), this test specifically measures the proportion of PSA that is not bound to proteins. Your doctor may recommend the Prostate Specific Antigen (Free) PSA test if you experience symptoms such as difficulty passing urine, straining or taking a long time while urinating, terminal dribbling, passing urine more frequently than usual, especially during the night, or blood in the urine. This test is also especially recommended in men over the age of 50 or at an earlier age (>40 years) for those at higher risk due to family history or other risk factors such as a high-fat diet.
Fasting is not required for this test; you may eat and drink as per your daily routine. However, talk to your doctor if you take any prescription or over-the-counter medications, as some may interfere with your test results. It is advised to avoid sexual intercourse for at least 48 hours before the test, as semen release (ejaculation) can increase your PSA levels, leading to inaccurate results. The Prostate Specific Antigen (Free) PSA test should also not be done immediately after cystoscopy, digital rectal examination (DRE), prostatic massage, indwelling catheterization, ultrasonography, and prostate needle biopsy as they too may falsely elevate PSA levels
Free PSA levels alone do not have much role in diagnosis and management. However, the ratio of free PSA to total PSA (percent free PSA) is an important indicator in the detection of prostate cancer. In individuals with elevated total PSA levels (4- 10 ng/ml), a high percent free PSA suggests a benign cause, while low percent free PSA values are more indicative of prostate cancer. Furthermore, while total PSA is used as a sensitive marker for prostate cancer recurrence after treatment, the Prostate Specific Antigen (Free) PSA test may not have much role in post-treatment monitoring.
Talk to your doctor about your specific test results. Regardless of levels, PSA values are not absolute evidence of the presence or absence of disease. Further diagnostic tests, such as digital rectal examination (DRE) and biopsy, may be needed to confirm or rule out the possibility of cancer. Values obtained with different assay methodologies should not be used interchangeably. It is recommended that only one assay method be used consistently to monitor the course of therapy.
What is Prostate Specific Antigen (Free) PSA used for?
The Prostate Specific Antigen (Free) PSA test is done:
- To screen for prostate cancer.
- To assess overall prostate health and detect benign diseases of the prostate gland like benign prostatic hyperplasia (BPH) or prostatitis.
- If you have symptoms of any prostate condition, such as painful or frequent urination, interrupted urine, blood in urine or semen, pelvic and/or back pain, or painful ejaculation.
What does Prostate Specific Antigen (Free) PSA measure?
The Prostate Specific Antigen (Free) PSA test measures the level of free prostate-specific antigen in the blood. PSA, a protein produced by prostate gland cells, circulates through the body in two ways: bound to other proteins or on its own. PSA circulating unbound in the blood is called free PSA. The total PSA test measures the total of both bound and free PSA, while the free PSA measures the level of unbound PSA alone.
Free PSA levels in the blood get affected in conditions affecting prostate health, such as prostate enlargement (benign prostatic enlargement or BPH) and prostate cancer. Prostate cancer does not show any symptoms in its early stages but may be fatal as it progresses to its advanced stages. Therefore, a free PSA test, along with other tests like total PSA, can be used as an early diagnosis and primary screening test for prostate health.
Interpreting Prostate Specific Antigen (Free) PSA results
Interpretations
The normal value of PSA (total) in blood is below 4.0 ng/ml
Total PSA levels roughly between 4.0 and 10.0 ng/ml are considered in “grey zone” and the probability of finding prostate cancer based on % free PSA in such cases is given below:
% free PSA |
Probability of prostate cancer |
0%–10% |
56% |
10%–15% |
28% |
15%–20% |
20% |
20%–25% |
16% |
Greater than 25% |
8% |
Some patients with a “normal” total PSA may have cancer. So, some doctors order both tests at the same time as a low total PSA and a low percentage of free PSA would probably indicates biopsy in these cases.