What is the PSA Test and why use it?

What is the PSA Test?

The prostate is a walnut-sized gland located below the bladder in a man’s reproductive system. This gland plays a role in semen production and helps propel sperm in the process of reproduction. The prostate produces a substance known as prostate-specific antigen, which is a protein. Low levels of PSA in the blood are normal, but a high level of PSA can indicate the presence of prostate inflammation, prostate cancer or prostate enlargement. Medical professionals use the PSA test, along with other information, to determine if a man has a benign prostate problem or prostate cancer.

Ordering Information

When a man has signs or symptoms of prostate cancer, prostate infection or prostate inflammation, his doctor might order the PSA test. The signs and symptoms of a prostate gland problem include the following:

• Pelvic pain
• Back pain
• Frequent urination
• Painful urination
• Difficulty urination

Testing Procedure

This simple test involves drawing a sample of blood from a vein in the arm. This causes relatively little discomfort, but those who are anxious about needles should discuss their concerns with a medical professional. A laboratory technician analyzes this blood sample to determine how much prostate-specific antigen is present. Men are advised to avoid ejaculation for at least 24 hours before the test, as it can alter the amount of PSA in the blood.

Results

Generally speaking, the normal value of PSA in the blood is less than 4.0 nanograms per milliliter (4.0 ng/ml). However, some laboratories use different reference ranges to determine what is normal and what is abnormal. Anyone who has a PSA test should discuss the results with a physician. The American Cancer Society says that a PSA level above 10.0 ng/ml indicates a more than 67 percent chance that a man has prostate cancer. PSA levels in between these two values may indicate benign conditions, but there is also a 25 percent chance that a man with a PSA level ranging from 4.0 to 10.0 ng/ml has prostate cancer.

There are variations on the PSA test that give more information about a man’s risk for prostate cancer. PSA velocity is a measure of PSA levels over time. If a man’s PSA increases significantly over two or three years, it is more likely that he has prostate cancer than a benign condition. If the PSA velocity increases quickly, the man might have a particularly aggressive form of prostate cancer. PSA doubling time provides similar information, except it is a measure of how quickly PSA doubles. Physicians also consider PSA density when determining a man’s cancer risk. Men with larger prostate glands tend to produce more prostate-specific antigen. PSA density compares the concentration of PSA in the blood with the volume of the prostate gland.

There are some factors that can alter PSA test results even if a prostate problem is not present. Any rigorous physical activity that affects the prostate can cause PSA levels to increase temporarily. If a man has had a prostate biopsy or resection of the prostate, PSA levels will be significantly increased. The PSA test should not be done until six weeks after the procedure to ensure accuracy. Some drugs used to treat cancer, such as methotrexate and cyclophosphamide, may also affect PSA levels. Because so many factors can alter PSA levels, many doctors will recheck any abnormal results before recommending a course of action. This can prevent the unnecessary surgery and complications associated with prostate cancer misdiagnosis.

Disease Detection

It is important to note that the PSA test does not detect all forms of prostate cancer. Some cancer cells do not produce excess prostate-specific antigen, so a PSA test will not always reveal an abnormality.