Prostate-Specific Antigen (PSA) Test
A prostate-specific antigen (PSA) test measures the amount of prostate-specific antigen in the blood. PSA is released into a man's blood by his prostate gland. Healthy men have low amounts of PSA in the blood. The amount of PSA in the blood normally increases as a man's prostate enlarges with age. PSA may increase because of inflammation of the prostate gland (prostatitis) or prostate cancer. An injury, a digital rectal exam, or sexual activity (ejaculation) may also briefly raise PSA levels.
Why It Is Done
The prostate-specific antigen (PSA) test is done to:
- Screen men for prostate cancer. Since other common medical conditions, such as benign prostatic hyperplasia (BPH) and prostatitis, can cause high PSA levels, a prostate biopsy may be done if your doctor is concerned about signs of prostate cancer.
- Check if cancer may be present when results from other tests, such as a digital rectal exam, are not normal. A PSA test does not diagnose cancer, but it can be used along with other tests to determine if cancer is present.
- Watch prostate cancer during active surveillance or other treatment. If PSA levels increase, the cancer may be growing or spreading. PSA is usually not present in a man who has had his prostate gland removed. A PSA level that rises after prostate removal may mean the cancer has returned or has spread.
How To Prepare
Do not ejaculate during the 2 days before your PSA blood test, either during sex or masturbation. Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean.
How It Is Done
A health professional uses a needle to take a blood sample, usually from the arm.
How It Feels
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
Because normal PSA levels seem to increase with age, age-specific ranges may be used. But the use of age-specific ranges is controversial, and some doctors prefer to use one range for all ages. For this reason, it is important to discuss your test results with your doctor.
A PSA level within the normal ranges does not mean that prostate cancer is not present. Some men who have prostate cancer have normal PSA levels.
A follow-up test that measures free prostate-specific antigen (free PSA) may be used to see if a prostate biopsy should be done to check for cancer. Free PSA is the percent of prostate-specific antigen that is not attached to proteins in the blood. The lower a man's free PSA percentage, the more likely he is to have prostate cancer.
A man with a total PSA between 4 and 10 ng/mL may have a test to find out his free PSA, to see if cancer is likely to be present. This test can be very useful if he had a negative prostate biopsy in the past but still has a high total PSA.
Current as of: December 17, 2020
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Christopher G. Wood MD, FACS - Urology, Oncology