PSA is determined from a sample of blood, and it can be used in different ways:
In men when it is not known whether they suffer from prostate cancer, as a screening or diagnostic test.
In men already diagnosed with prostate cancer, as a specific marker or monitoring procedure.
PSA (prostate-specific antigen), a protein that liquefies semen, is secreted by prostate and used as a tumour marker.
This substance is found only in the prostate and only in men, and it is a tumour marker in men starting at age 50, when a certain amount of this protein is present in the bloodstream.
PSA can be found in blood a free form, or bound to other blood substances.
When in the free form, it is known as free PSA.
▪ When bound to other substances, it is known as complexed PSA.
▪ The total PSA is the sum of both forms of PSA, which is regularly determined in blood tests.
When PSA determination is used as a screening or diagnostic test, if an abnormal result is observed then additional tests will be required. Increased levels of PSA may suggest the presence of prostate cancer.