What Is a PSA Test?

The prostate-specific antigen blood test (PSA) is a screening test that measures the amount of this antigen in a man's blood. This substance is produced by the prostate gland. Elevations of PSA may indicate prostate cancer or a benign condition such as an enlarged prostate or inflamed prostate (prostatitis).

Significance

• The U.S. Food and Drug Administration (FDA) has approved the use of the PSA test along with a digital rectal exam (DRE) to help detect prostate cancer in men 50 years of age or older. Most screening begins at age 50, however, some men are screened earlier including African American men beginning at 40 and men who have a family history of prostate cancer in the family.

Function

• According to the Mayo Clinic, prostate cancer is the second most common cancer in men after skin cancer. This test is somewhat controversial since in some men high levels of PSA may indicate cancer, however, other benign conditions may also increase the PSA levels as well. Therefore, this test doesn't provide enough diagnostic information.
  The PSA blood test is only one tool used to screen for prostate cancer. The digital rectal exam is very important as some men may have a normal PSA test and yet still have conditions of the prostate gland. A physician inserts a lubricated gloved finger into the rectum to feel the prostate gland. He then feels to determine if the gland is enlarged or has abnormal lumps. Sometimes a biopsy of the prostate tissues is the only conclusive way to diagnose cancer.

Features

• The PSA blood test is also used to monitor men who already have been diagnosed with prostate cancer. Changes in the values may monitor any changes in the tumor, determine if the treatments have been effective and also check for recurring cancer.

Results

• Since normal PSA levels have a tendency to increase with age, labs use age-specific ranges. Some doctors feel that this practice is controversial and tend to use one range for all. PSA levels in the blood are reported as nanograms of PSA per milliliter (ng/mL). Labs consider a value lower than 4.0 ng/mL as normal, however, only a doctor can make the final decision what is normal for the patient after evaluating all other tests.

Considerations

• There are factors that can affect the accuracy of a PSA blood test:
  • Recent sexual activity with ejaculation
  • Tests such as a cystoscopy or use of a catheter (tube) to drain the urine
  • Recent urinary tract infection or prostatitis
  • Medications, such as those used for prostate cancer treatment or to prevent further enlargement of the prostate gland in men.
  It is best to draw a PSA blood test before sexual activity, before undergoing urologic procedures or after an infection has cleared. Check with the physician about the medications you take before undergoing this blood test.