Description
Prostate-specific antigen (PSA), also known as gammaseminoprotein or kallikrein-3 (KLK3), is a kallikrein-like protease produced by the epithelial cells in the prostate gland, the lining of the urethra, and the bulbourethral gland1. It is a single-chain glycoprotein with a molecular weight of 30-33 kDa in human seminal plasma and it functions normally in the liquefaction of seminal coagulum2-3. Under normal conditions, very little PSA is secreted in the blood. PSA exists in serum in multiple forms. The proteolytic activity of PSA in blood is inhibited by irreversible formation of complexes with proteinase inhibitors such as alpha-1-antichymotrypsin (PSA-ACT complex), alpha-2-macroglobulin and other acute phase proteins1-3. A small amount of PSA is not protein bound and is called "free PSA", which is proteolytically inactive4. Increases in glandular size and tissue damage caused by benign prostatic hypertrophy, prostatitis, or prostate cancer may increase circulating total PSA levels5. Monitoring the total PSA level in male blood has been used as an indicator for abnormal prostate function in the past decades. This assay provides an equal molar detection on different forms of PSA in human matrices, which improves the accuracy and sensitivity of the measurement on the total PSA levels6-7