PSA Test (Prostate Specific Antigen)

  • Medical Author: Pamela I. Ellsworth, MD
  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

4KScore Test

The 4K biomarker is a blood test that measures four different proteins in the blood to assess prostate cancer risk. The blood test that assesses these biomarkers is called the 4KScore Test. It suggests the possible risk that a significant prostate cancer would be found.

The 4Kscore Test relies on the measurement of four prostate-specific kallikreins in the blood:

  • Total PSA,
  • Free PSA,
  • Intact PSA, and
  • Human Kallikrein 2 (hK2).

Quick GuideScreening Tests Every Man Should Have

Screening Tests Every Man Should Have

Prostate-specific antigen (PSA) test facts

  • The PSA test is a blood test.
  • The PSA test can be useful for detecting prostate cancer, monitoring its treatment, or assessing its recurrence.
  • The PSA test can also be abnormal with benign enlargement (benign prostatic hyperplasia or BPH), inflammation (prostatitis), and infection of the prostate gland.
  • PSA is a chemical that is produced by both cancerous and noncancerous prostate tissues.
  • Prostate cancer is the third leading cause of death in men. Both the disease and its treatment may have a significant impact on men's health. Thus, accurate screening tools to detect clinically significant prostate cancer are needed.

What is a PSA blood test?

Prostate-specific antigen (PSA) is a substance produced only by certain cells within the male prostate gland. Biochemically, it belongs to the protease family of kallikrein and is also known as human kallikrein 3 (hK3). PSA is released by the prostate into the semen where it acts to liquefy the semen following ejaculation. Most of the PSA produced by the prostate gland is carried out of the body in semen, but a very small amount escapes into the bloodstream, so PSA is normally found in low amounts (nanograms per milliliter or ng/mL) in the blood. PSA has also been found in some breast tissue in women, although these amounts of PSA are very low.

If the PSA level is high for your age or is steadily increasing (with or without an abnormal physical exam), further investigation, namely a prostate biopsy, may be recommended. The health care provider should consider other health risk factors of prostate cancer such as family history, prostate volume, the presence of benign prostatic hyperplasia (BPH), urinary symptoms, rectal exam findings, ethnicity, and medications that you are taking before recommending the biopsy. At this time, prostate biopsy for pathology review is the only way to determine if prostate cancer or other abnormal cells are present in the prostate.

Medically Reviewed by a Doctor on 2/1/2017

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