PSA

Alternative names
Prostate-specific antigen

Definition
The PSA test measures the amount of PSA (prostate-specific antigen) in the blood.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

How to prepare for the test

No special preparation is usually necessary, but men who engage in sexual intercourse within 24 hours before the PSA test may have a falsely elevated result. Falsely elevated results can also be due to a recent urinary tract infection or a recent surgery on the urinary tract.

Discuss with your doctor or health care provider whether a PSA test is appropriate for you, because it is not appropriate for all men.

How the test will feel

When the needle is inserted to draw blood, some people feel moderate pain while others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a bruise.

Why the test is performed

This test is performed to detect the presence of PSA.

PSA is a glycoprotein (a protein with a sugar attached) found in prostatic epithelial cells. It can be detected at a low level in the blood of all adult men.

The PSA level is elevated in men with BPH (benign prostatic hypertrophy) and Prostate cancer. Other inflammatory diseases, such as prostatitis, may also increase the PSA level.

Normal Values


Normal Values
vary with age. Older men typically have slightly higher PSA measurements than younger men. African-Americans normally have slightly higher values than white men.

A PSA of 4 ng/ml is typically used to determine the need for further evaluation with a prostate biopsy. Keep in mind that while the PSA test is an important tool for detecting Prostate cancer, it is not foolproof. A PSA test does not always detect the presence of cancer. A digital rectal exam should also be performed to check for Prostate cancer.

Note: ng/ml = nanograms per milliliter

What abnormal results mean

Greater-than-normal levels may indicate:

What the risks are

     
  • Fainting or feeling light-headed  
  • Hematoma (blood accumulating under the skin)  
  • Infection (a slight risk any time the skin is broken)  
  • Multiple punctures to locate veins

Special considerations

Starting at age 50, you should talk to your provider at your regular physical to see whether PSA testing is appropriate for you. PSA testing may be started at age 40 or 45 if you have risk factors for Prostate cancer, like you are African American or you have a father or brother diagnosed at an early age.

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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