PSA

Definition

PSA stands for prostate-specific antigen. It is a protein with a sugar molecule attached that is found in prostate cells. It can be detected at a low level in the blood of all adult men.

This article discusses the blood test to measure the amount of PSA in a man's blood.

Alternative Names

Prostate-specific antigen; Prostate cancer screening test 

Why the Test is Performed

This test is done to screen for prostate cancer and other conditions. Several conditions besides cancer can cause the PSA level to rise. These include urinary tract infections, benign prostatic hyperplasia, and prostatitis.

Discuss with your doctor or health care provider whether a PSA test is appropriate for you.

How the Test is Performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. 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 needed.

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.

Risks

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Considerations

The American Urologic Association, the American Cancer Society, and the National Comprehensive Cancer Network recommend that all men have annual PSA tests beginning at age 50.

Testing is recommended at an earlier age (age 40 or 45) if you have any of the following risk factors:

• African American heritage
• Father or brother with prostate cancer

However, these guidelines are not universal. Many health organizations do not recommend routine PSA testing.

You should discuss the benefits and risks of testing with your doctor.

Potential benefits include early diagnosis of cancer with better chance of cure.

Potential risks include increased health care costs, unnecessary invasive testing (biopsy), and unnecessary treatment. Weigh these factors to determine if routine screening is right for you.

Normal Results

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.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

A high PSA level has been linked to an increased chance of having prostate cancer. However, a high PSA level does not mean that you definitely have prostate cancer. A high PSA level only identifies patients at higher risk of having prostate cancer. People at higher risk may need to have more tests.

A PSA of 4 nanograms per milliliter (ng/mL) is abnormally high for most men and may indicate the need for a prostate biopsy.

Keep in mind that although PSA testing is an important tool for detecting prostate cancer, it is not foolproof.

Greater-than-normal PSA levels may indicate:

• Benign prostatic hypertrophy
• Prostate cancer
• Prostatitis
• Prostate infection
• Urinary tract infection
• Recent urinary catheterization
• Recent urinary tract operation