Prostate-specific antigen (PSA) is an enzyme made by the prostate gland of adult men. Small amounts of PSA are normally released into the bloodstream. When the prostate is enlarged, infected or diseased, larger amounts of PSA are released. The level of PSA in the blood can be determined by a simple blood test.
Why might I need this test?
The PSA test may be done to screen for cancer. Men with prostate cancer may have high levels of PSA. However, the test is not always accurate. PSA level can be raised by benign conditions, or it may be normal even when prostate cancer is present.
PSA testing can also be used to monitor the course of prostate cancer or monitor and evaluate a patient's response to treatment.
How do I prepare for this test?
No special preparation is needed for this test. In order to prevent a falsely elevated result, your doctor may recommend that you have the PSA test either prior to, or at least 48 hours after, a DRE.
How is this test performed?
A technician, doctor, or nurse will begin by using an antiseptic to clean the skin above a vein on your arm. A blood sample will then be drawn. You may feel a brief pricking sensation when the needle is initially inserted. The blood sample will be collected into a tube and then sent to a lab for analysis.
How long does the procedure take?
Obtaining blood for a PSA blood test takes between three and five minutes.
What happens if an abnormality is found?
If your PSA results are slightly elevated and the DRE was normal, your doctor may repeat the PSA test to see if it remains high.
An elevated PSA above 4 ng/mL (nanograms per milliliter) may indicate a 20 percent to 25 percent possibility of prostate cancer. If your PSA level is above 10 ng/mL, your chance of having prostate cancer is higher than 50 percent and increases further as your PSA level rises.
However, PSA results alone do not confirm a diagnosis of prostate cancer. Other conditions can cause elevated PSA levels. An enlarged prostate, a condition called benign prostate hyperplasia, can raise PSA levels two to three times higher than normal. An infected or inflamed prostate, and a biopsy or operation on the prostate, can also raise your PSA levels.
If your PSA results are high, further assessment and testing may include a transrectal ultrasound. A tissue biopsy is needed to make the diagnosis of prostate cancer.
Are there any risks associated with this test?
There are practically no risks associated with the blood test, itself. Although, there is always the concern that a false positive test might generate additional tests and anxiety. Alternatively, a false negative test might lead to delay in further evaluation for prostate cancer.
What is a desirable result?
Most men age 40 or older should have PSA levels under 4 ng/mL of blood. Ideally, PSA levels for men under age 40 should be less than 2.7 ng/mL.
