A prostate-specific antigen (PSA) test measures the level of PSA in a man’s blood. PSA is a protein produced by the cells of your prostate, a small gland just underneath your bladder. PSA circulates through your entire body at low levels at all times.
A PSA test is sensitive and can detect higher-than-average levels of PSA. High levels of PSA may be associated with prostate cancer before any physical symptoms appear. However, high levels of PSA may also mean you have a noncancerous condition that’s increasing your PSA levels.
According to the Centers for Disease Control and Prevention (CDC), prostate cancer is the most common cancer among men in the United States, other than non-melanoma skin cancer.
A PSA test alone doesn’t provide enough information for your doctor to make a diagnosis. However, your doctor can take the results of a PSA test into consideration when trying to decide whether your symptoms and test results are due to cancer or another condition.
PSA tests are controversial because doctors and experts aren’t sure if the benefits of early detection outweigh the risks of misdiagnosis. It’s also not clear if the screening test actually saves lives.
Because the test is very sensitive and can detect increased PSA numbers at low concentrations, it may detect cancer that’s so small it would never become life-threatening. Just the same, most primary care physicians and urologists do choose to order the PSA as a screening test in men over the age of 50.
This is called overdiagnosis. More men may face complications and risks of side effects from the treatment of a small growth than they would if their cancer was left undiagnosed.
It’s doubtful those small cancers would ever cause major symptoms and complications because prostate cancer, in most but not all cases, is a very slow-growing cancer.
There’s also no specific level of PSA that’s considered normal for all men. In the past, doctors considered a PSA level of 4.0 nanograms per milliliter or lower to be normal, reports the National Cancer Institute.
However, recent research has shown that some men with lower levels of PSA have prostate cancer and many men with higher levels of PSA don’t have cancer. Prostatitis, urinary tract infections, certain medications, and other factors can also cause your PSA levels to fluctuate.
Several organizations, including the U.S. Preventive Services Task Force, now recommend that men aged 55 to 69 decide for themselves whether to undergo a PSA test, after talking it over with their doctor. Screening after age 70 is not recommended.
All men are at risk of prostate cancer, but a few populations are more likely to develop it. These include:
- older men
- African-American men
- men with a family history of prostate cancer
Your doctor may recommend a PSA test to screen for early signs of prostate cancer. According to the American Cancer Society, you doctor can also use a digital rectal exam to check for growths. In this exam, they’ll place a gloved finger into your rectum to feel your prostate.
In addition to testing for prostate cancer, your doctor may also order a PSA test:
- to determine what’s causing a physical abnormality on your prostate found during a physical exam
- to help decide when to begin treatment, if you’ve been diagnosed with prostate cancer
- to monitor your prostate cancer treatment
If your doctor requests that you have a PSA test, make sure that they’re aware of any prescription or over-the counter medicines, vitamins, or supplements you take. Certain drugs may cause the test results to be falsely low.
If your doctor thinks your medication might interfere with the results, they may decide to request a different test or they may ask you to avoid taking your medicine for several days so your results will be more accurate.
A sample of your blood will be sent to a laboratory for further examination. To withdraw blood from an artery or vein, a healthcare provider will usually insert a needle into the inside of your elbow. You may feel a sharp, piercing pain or slight sting as the needle is inserted into your vein.
Once they’ve collected enough blood for the sample, they will remove the needle and hold pressure on the area to stop the bleeding. They’ll then put an adhesive bandage over the insertion site in case you bleed more.
Your blood sample will be sent to a laboratory for testing and analysis. Ask your doctor if they’ll follow up with you regarding your results, or if you should make an appointment to come in and discuss your results.
Drawing blood is considered safe. However, because veins and arteries vary in size and depth, getting a blood sample isn’t always simple.
The healthcare provider who draws your blood may have to try several veins in multiple locations on your body before they find one that allows them to get enough blood.
Drawing blood also has several other risks. These include risk of:
- excessive bleeding
- feeling lightheaded or dizzy
- an infection at the puncture site
- a hematoma, or blood collected under the skin, at the puncture site
A PSA test can also produce false-positive results. Your doctor may then suspect you have prostate cancer and recommend a prostate biopsy when you don’t actually have cancer.
If your PSA levels are elevated, you’ll likely need additional tests to learn the cause. Other than prostate cancer, possible reasons for a rise in PSA include:
- a recent insertion of a catheter tube into your bladder to help drain urine
- recent testing on your bladder or prostate
- a urinary tract infection
- prostatitis, or an inflamed prostate
- an infected prostate
- benign prostatic hyperplasia (BPH), or an enlarged prostate
If you have an elevated risk of prostate cancer or your doctor suspects you may have prostate cancer, a PSA test can be used as part of a larger group of tests to detect and diagnose prostate cancer. Other tests you may need include:
What are common symptoms of prostate cancer that I should watch out for?
While the early stages of prostate cancer often have no symptoms, clinical signs do tend to develop as the cancer advances. Some of the more common symptoms include: difficulty with urination (e.g., hesitation or dribbling, poor urine flow); blood in the semen; blood in the urine (hematuria); pelvic or rectal area pain; and erectile dysfunction (ED).Steve Kim, M.D.Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.