Prostate-Specific Antigen (PSA)
Prostate-specific antigen (PSA) is a protein produced by cells of the prostate gland. PSA functions in male fertility, and most of it gets expelled from the body in semen. However, low levels circulate in the blood. Elevated serum PSA levels often indicate the presence of prostate cancer and other prostate disorders.
The PSA screening test measures the total level of PSA circulating in the blood serum. PSA levels above 4 ng per milliliter are considered above normal. However, total PSA does not offer a definitive diagnosis for cancer or other prostate disease. Therefore, additional measures of PSA have been integrated to depict a more comprehensive profile of prostate disease characteristics. For example, PSA velocity measures the rate of increase in PSA over time. Generally, larger PSA velocity is associated with prostate cancer. Free PSA is the percentage of circulating PSA that is not...
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