Prostate-specific antigen (PSA) blood test
Prostate-specific antigen; Prostate cancer screening test; PSA
Prostate-specific antigen (PSA) is a protein produced by prostate cells.
The PSA test is done to help screen for and follow prostate cancer in men.
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
Make sure your health care provider knows all the medicines you are taking. Some drugs cause your PSA level to be falsely low.
In most cases, no other special steps are needed to prepare for this test. You should not have a PSA test soon after having a urinary tract infection or undergoing a procedure or surgery involving the urinary system. Ask your provider how long you should wait.
How the Test will Feel
You may feel slight pain or a prick when the needle is inserted. Afterward, there may be some throbbing or a slight bruise. These soon go away.
Why the Test is Performed
Reasons for a PSA test:
- This test may be done to screen for prostate cancer.
- It is also used to follow people after prostate cancer treatment to see if the cancer has come back.
- If a provider feels the prostate gland is not normal during physical exam.
MORE ABOUT SCREENING FOR PROSTATE CANCER
Measuring the PSA level can increase the chance of finding prostate cancer when it is very early. But there is debate over the value of the PSA test for detecting prostate cancer. No single answer fits all men.
For some men 55 through 69 years old, screening may help reduce the chance of death from prostate cancer. However, for many men, screening and treatment could potentially be harmful instead of beneficial.
Before having the test, talk to your provider about the pros and cons of having a PSA test. Ask about:
- Whether screening decreases your chance of dying from prostate cancer
- Whether there is any harm from prostate cancer screening, such as side-effects from testing or overtreatment of cancer when discovered
Men younger than age 55 have a higher chance of developing prostate cancer and should talk with their provider about PSA screening if they:
- Have a family history of prostate cancer (especially a brother or father)
- Are African American
As men get older, they have a lot of new worries to deal with, from hair loss, weight gain, perhaps even erectile dysfunction. In addition, cancer is one of the biggest concerns that older men face, especially prostate cancer, which is the leading cause of cancer death in men over 75. Younger men may not be very familiar with their prostate, the walnut-shaped gland that wraps around the urethra, the tube that carries urine out of the body. But as they get older, the prostate can start to cause problems. Men over the age of 60 are at increased risk for prostate cancer, especially if they're of African descent, they have a father or brother with the disease, or they eat a lot of burgers and processed meats in their daily diet. It can be hard to pinpoint prostate cancer symptoms, because they usually start late in the disease and they can mimic symptoms of a benign, enlarged prostate, which is also more common in older men. Symptoms like a slow urine stream, dribbling, blood in the urine, or straining while urinating can be signs of either condition. An enlarged prostate can also confuse the results of a PSA test, which is used to screen for prostate cancer. So, if your doctor thinks you might have prostate cancer, you may need a biopsy, which is a procedure that removes a small piece of prostate tissue and sends it to the lab to check for cancer. Then a scoring system called the Gleason grade is used to tell how fast your cancer might spread. Your Gleason grade will help decide what treatment you get. Early-stage prostate cancers that haven't spread are often removed with surgery, and then treated with radiation therapy to kill any remaining cancer cells. Prostate cancer surgery may affect your ability to have sex and control urine, so talk about these issues with your doctor before you have the procedure. Because prostate cancer tends to grow very slowly, your doctor may want to just monitor you with PSA tests and biopsies, and avoid treatment unless the cancer starts to spread. Prostate cancer that has spread is usually treated with surgery, chemotherapy, or hormone therapy. If your doctor discovers prostate cancer in its early stages, before it spreads, it's pretty easy to treat, and even cure. Treatments can also slow down prostate cancer that's spread, and extend your survival. Before you have to deal with a prostate cancer diagnosis, ask your doctor for ways to prevent and screen for the disease. Eating a healthy, low-fat diet that's high in healthy omega-3 fatty acids might help lower your risk. There are also drugs called finasteride and dutasteride that are used in some men to prevent prostate cancer. Talk with your doctor about the pros and cons of these drugs, as well as the possible benefits and risks of having your PSA levels tested.
The PSA test result cannot diagnose prostate cancer. Only a prostate biopsy can diagnose this cancer.
Your provider will look at your PSA result and consider your age, ethnicity, medicines you are taking, and other things to decide whether your PSA is normal and whether you need more tests.
A normal PSA level is considered to be 4.0 nanograms per milliliter (ng/mL) of blood, but this varies by age:
- For men in their 50s or younger, a PSA level should be below 2.5 in most cases.
- Older men often have slightly higher PSA levels than younger men.
What Abnormal Results Mean
A high PSA level has been linked to an increased chance of having prostate cancer.
PSA testing is an important tool for detecting prostate cancer, but it is not foolproof. Other conditions can cause a rise in PSA, including:
- A larger prostate
- Prostate infection (prostatitis)
- Urinary tract infection
- Recent tests on your bladder (cystoscopy) or prostate (biopsy)
- Catheter tube recently placed into your bladder to drain urine
- Recent intercourse or ejaculation
- Recent colonoscopy
Your provider will consider the following things when deciding on the next step:
- Your age
- If you had a PSA test in the past and how much and how fast your PSA level has changed
- If a prostate lump was found during your exam
- Other symptoms you may have
- Other risk factors for prostate cancer, such as ethnicity and family history
Men at high risk may need to have more tests. These may include:
- Repeating your PSA test, most often sometime within 3 months. You may receive treatment for a prostate infection first.
- A prostate biopsy will be done if the first PSA level is high, or if the level keeps rising when the PSA is measured again.
- A follow-up test called a free PSA (fPSA). This measures the percentage of PSA in your blood that is not bound to other proteins. The lower the level of this test, the more likely it is that prostate cancer is present.
Other tests may also be done. The exact role of these tests in deciding on treatment is unclear.
- A urine test called PCA-3.
- An MRI of the prostate may help identify cancer in an area of the prostate that is hard to reach during a biopsy.
If you have been treated for prostate cancer, the PSA level can show if treatment is working or if the cancer has come back. Often, PSA level rises before there are any symptoms. This may happen months or years beforehand.
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others. Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Multiple punctures to locate veins
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Morgan TM, Palapattu GS, Partin AW, Wei JT. Prostate cancer tumor markers. In: Wein AJ, Kavoussi LR, Partin AW, Peters CA, eds. Campbell-Walsh Urology. 11th ed. Philadelphia, PA: Elsevier; 2016:chap 108.
National Cancer Institute website. Prostate cancer screening (PDQ) - health professional version.
Small EJ. Prostate cancer. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 191.
US Preventive Services Task Force; Grossman DC, Curry SJ, et al. Screening for prostate cancer: US Preventive Services Task Force recommendation statement. JAMA. 2018;319(18):1901-1913. PMID: 29801017
Last reviewed on: 1/15/2020
Reviewed by: Sovrin M. Shah, MD, Assistant Professor, Department of Urology, The Icahn School of Medicine at Mount Sinai, New York, NY. Review provided by VeriMed Healthcare Network. Internal review and update on 06/03/2021 by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.