Prostate-specific antigen

Prostate-specific antigen (PSA) is a protein produced mainly by prostate cells that helps liquefy semen and can be measured in blood.

Kallikrein-related peptidase 3: Kallikrein-related peptidase 3 is the gene encoding prostate-specific antigen, a serine protease. This gene encodes the protein measured in PSA tests.
Prostate cancer screening: Prostate cancer screening tests people without symptoms to estimate the chance of cancer. Blood PSA is a commonly offered screening test, with benefits and harms to weigh.
Prostate health index: The prostate health index combines total PSA, free PSA, and [-2]proPSA into a risk score. It combines PSA forms to refine estimates of clinically significant cancer risk.
PSA density: PSA density is the blood PSA concentration divided by prostate volume. It adjusts PSA interpretation for gland size, which can affect concentration.
Semen liquefaction: Semen liquefaction is the enzymatic breakdown of semen’s temporary gel after ejaculation. PSA helps dissolve the seminal coagulum after ejaculation.
Prostate biopsy: A prostate biopsy removes tissue samples for microscopic examination. An elevated PSA can contribute to deciding whether biopsy is appropriate.
PCA3: PCA3 is a prostate-associated RNA measured in urine as a marker related to prostate cancer. Unlike blood PSA, PCA3 testing measures prostate-derived RNA in urine.
Free-to-total PSA ratio: The free-to-total PSA ratio compares unbound PSA with total PSA in blood. The ratio can help refine risk estimates when total PSA is borderline.
Prostate: The prostate is a gland below the bladder that contributes fluid to semen. Prostate tissue is the principal source of circulating PSA.
Prostate cancer: Prostate cancer is a malignancy arising in the prostate, most often from glandular cells. PSA can signal prostate cancer, but it cannot diagnose it by itself.

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