Description
Prostate-specific antigen (PSA) is a glycoprotein that is produced by the prostate gland, the lining of the urethra, and the bulbourethral gland. Normally, very little PSA is secreted in the blood. Increases in glandular size and tissue damage caused by benign prostatic hypertrophy, prostatitis, or prostate cancer may increase circulating PSA levels.Elevated serum PSA concentrations have been reported in men with prostate cancer, benign prostatic hypertrophy, and inflammatory conditions of the prostate.
Higher total PSA levels and lower percentages of free PSA are associated with higher risks of prostate cancer.Most prostate cancers are slow growing, so the utility of prostate cancer screening is marginal in most men with a life expectancy of less than 10 years.When total prostate-specific antigen (PSA) concentration is below 2.0 ng/mL, the probability of prostate cancer in asymptomatic men is low, further testing and free PSA may provide little additional information. When total PSA concentration is above 10.0 ng/mL, the probability of cancer is high and prostate biopsy is generally recommended.The total PSA range of 4.0 to 10.0 ng/mL has been described as a diagnostic "gray zone," in which the free:total PSA ratio helps to determine the relative risk of prostate cancer . Therefore, some urologists recommend using the free:total ratio to help select which men should undergo biopsy. However, even a negative result of prostate biopsy does not rule-out prostate cancer. Up to 20% of men with negative biopsy results have subsequently been found to have cancer.
A total PSA test 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.Total PSA ranges may vary slightly. According to a review of studies, the normal ranges for total PSA in nanograms per milliliter (ng/mL) are:
age 49 or younger: 0.0–2.5 ng/mL
age 50 to 59: 0.0–3.5 ng/mL
age 60 to 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. Hence comparison of the results of this test with results of a free PSA test can lead to proper conclusion.
