PSA Test (Prostate Specific Antigen)

  • Medical Author:
    Kevin C. Zorn, MD, FRCSC, FACS

    Dr. Kevin Zorn is a dual-board-certified (US and Canada), minimally-invasive uro-oncology, fellowship trained urologist at the University of Chicago. His main focus of clinical and scientific interest is in the surgical treatment of renal and prostate cancer. He is also an expert in performing surgery with the DaVinci Surgical Robotic System to manage localized prostate cancer and small renal masses. Dr. Zorn studied medicine and urology at McGill University in Montréal.

  • Medical Author: Pierre-Alain Hueber, MD, PhD
  • 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.

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What are the limitations of the PSA test?

The level of PSA is a continuous parameter; the higher the value, the higher the probability of having prostate cancer. On the other hand, men may have prostate cancer despite low levels of PSA. In a U.S. prevention study, 6.6% of the men whose PSA level was less than 0.5 ng/mL had prostate cancer. This is why there is no universally accepted cutoff at which we can be sure that there is no prostate cancer. Coupled with the lack of an accurate molecular marker to detect prostate cancer, the other controversy with PSA screening is the fact that not all men with prostate cancer will die from the disease (See: What is the PSA screening controversy?).

For these reasons outlined above, it is important to not solely rely on blood PSA testing. The most useful additional test is a physical prostate examination by a doctor known as the digital rectal exam (DRE). Evidence from research studies suggests that the combination of both PSA and DRE improves the overall rate of prostate cancer detection. For that reason, men who would like to be screened for prostate cancer should have both a prostate specific antigen (PSA) test and a digital rectal examination (DRE).

What is digital rectal examination (DRE)?

Most prostate cancers are located in the peripheral zone of the prostate and may be detected by DRE. During this examination a doctor inserts a finger into the rectum to feel the prostate for lumps, size, shape, tenderness, and hardness. A suspect DRE is an absolute indication for prostate biopsy. In about 18% of patients with abnormal DRE, prostate cancer will be detected regardless of the PSA level.

Medically Reviewed by a Doctor on 1/14/2016

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