What Is the Prostate-Specific Antigen (PSA) Test?

What to expect when undergoing this test

The prostate-specific antigen (PSA) test is a screening test for prostate cancer, as well as a method for monitoring the treatment of the disease and testing for recurrence. Like other early detection cancer screening tests, it is designed to alert a person to the presence of disease before any symptoms occur. At the current time, most prostate cancers are detected in this way, via this blood test and a digital rectal exam. In recent years, however, the PSA test has become controversial.

A 2018 review for the U.S. Preventive Services Task Force concluded that PSA screening may reduce deaths due to prostate cancer, but also carries the risk of complications of diagnosis, as well as overdiagnosis and overtreatment of cases that would never have, otherwise, caused a problem. While prostate cancer tends to be slow-growing and has a high survival rate relative to many cancers, it remains the most common cancer (other than skin cancer) and is the second leading cause of cancer-related deaths in men.

What can cause an elevated TSA
Illustration by Cindy Chung, Verywell 

Purpose of Test

The PSA test may be used either for screening or to evaluate the progress of a known prostate cancer. It checks for the blood level of prostate-specific antigen, a protein secreted only by prostate cells with the function of liquefying semen. PSA is produced by both normal and cancerous prostate cells, though it may be released in greater amounts by cancer cells.

Screening and Evaluation of Symptoms

The prostate-specific antigen test was approved in 1994 as a screening for prostate cancer in men who have no signs of the disease. It may also be done to evaluate men who have signs and symptoms of prostate cancer or risk factors for the disease.

While in the past men at average risk were encouraged to have a PSA test beginning at age 50 (along with a digital rectal exam), different organizations now have varying guidelines, with some recommending that the test be skipped altogether.

Monitoring Prostate Cancer

The PSA test was first used as a method of monitoring the progress of prostate cancer during treatment and is still the case today. It is also done to screen for recurrence of the disease after treatment.

Limitations and Concerns

There has been significant controversy in recent years regarding the limitations of the PSA test, specifically as they relate to results.

  • False positives: PSA levels may be elevated due to reasons other than prostate cancer, including age, inflammation of the prostate (prostatitis), and enlarged prostate (benign prostatic hyperplasia). Recent intercourse, strenuous exercise, a urinary tract infection, and testing done after a digital rectal exam or when a Foley catheter is in place can also throw off results.
  • False negatives: Levels of PSA in the "normal range" do not guarantee that a prostate cancer is not present. In addition, obesity and some medications for BPH can reduce PSA levels.

Even when a prostate cancer is found based on a PSA test and further tests, it may not reduce the risk of death related to the tumor (but may reduce the quality of life). It's estimated that between 23 percent and 42 percent of men who are diagnosed with prostate cancer based on the results of PSA screening would not develop symptoms of the disease during their lifetime. At the same time, a significant number of these men may end up coping with side effects of treatment (whether surgery, radiation therapy, or others), such as incontinence and erectile dysfunction.

Similar Tests

There are a number of variations and ways to assess PSA today. These newer tests—some of which may be done as add-on assessments of the same sample, others performed separately after a traditional PSA test—are being developed and evaluated as ways to improve the accuracy of screening and monitoring:

  • PSA velocity: PSA velocity is a measure of how fast the PSA level is changing. While a change in PSA over time is often considered to be of greater concern than the absolute level of PSA, the role of this test in screening for prostate cancer is still uncertain. While it may be used for screening (to see if further testing is needed), it is often used to see if a known prostate cancer has progressed.
  • PSA doubling time: PSA doubling time is another way to look at PSA velocity. For example, a rapid doubling time of PSA, or a rise of 035 ng/mL or more in a year, may signal a rapidly growing cancer regardless of the absolute level of the PSA.
  • Free PSA: PSA travels in the blood both freely and bound to proteins. A low percent of free PSA (less than 10 percent) raises the likelihood that prostate cancer is present, whereas a high PSA (more than 25 percent) suggests that it is not. Many values, however, fall between these numbers.
  • PSA density: This number compares the amount of PSA to the size of the prostate on MRI or ultrasound, as cancers usually make more PSA per volume of tissue than normal prostate cells. This test is somewhat limited as a prostate ultrasound or MRI are needed to make the comparison.
  • Pro-PSA: A pro-PSA may be done when a PSA is between 4 and 10 to help discriminate an elevated PSA due to BPH from that due to cancer.
  • Age-specific PSA: Age may be considered when evaluating PSA, as PSA levels often rise with age.
  • Biomarkers combined with PSA: Other tests may be combined with a PSA to improve the predictive value. A test called PCA3 is urine test done to look for a fusion of genes common in men with prostate cancer. Other biomarkers are also being evaluated, such as kallikrein-related peptidase 3 and the TMPRSS2-ERG gene.

Whether or not these tests are performed depends on the doctor overseeing one's care, the lab, and/or the patient's health profile.

Other Tests

Most physicians believe that the PSA test should be done in conjunction with a digital rectal exam, and that neither of the tests should be used alone. Due to the proximity of the prostate gland to the rectum, a digital rectal exam allows physicians to palpate the gland for evidence of masses, firmness, and more.

Risks and Contraindications

Like any medical test, there are potential risks related to checking a PSA, as well as reasons not to do the test.

Potential Risks

The primary risks of a PSA test are related to false negative and false positive results. With a false negative result, a low PSA level may give false confidence that cancer is not present when it is. False positive results are usually of even greater concern. False positives may lead to the overdiagnosis and overtreatment, and all of the risks related to diagnostic procedures (such as biopsies), and well as treatments (such as surgery). The emotional risk that goes along with a false positive result can also not be understated.

Contraindications

A PSA test, at least in men of average risk, is not usually recommended before the age of 40. In addition, screening should, in general, be avoided for men who are not expected to live for at least 10 to 15 years, as most prostate cancers are slow growing, and the risk of treatments for an "average" prostate cancer is likely to exceed any potential benefits.

Before the Test

Before you have a PSA test, it's important that you talk with your doctor about the risks and benefits of the test, as well as what might be expected if the test is abnormal. Understanding the limitations of the test and making an educated decision about whether the test should be done in your case are crucial to minimizing the associated risks.

A doctor will also look at your risk factors for prostate cancer such as a family history of the disease, as well as any possible prostate cancer symptoms you are having.

Timing

The actual PSA test is a simple blood draw and should take less than five minutes to perform. It usually takes a few days for a primary care physician to receive the results of the test and to pass on the information to you. If you have not received your results, don't assume they are normal.

Location

A PSA test can be done at most clinics. The blood sample may be run at the clinic itself or sent out to a lab.

What to Wear

You can wear normal clothing to have your PSA drawn, although having a shirt that unbuttons easily at the wrist to expose the veins in your arm is helpful.

Food and Drink

There are no dietary restrictions needed prior to a PSA test.

Physical and Sexual Activity

Since ejaculation may increase PSA levels, doctors often recommend avoiding it for a day or two prior to the test. Vigorous activity may also result in increased PSA and should be minimized in the day or two before testing.

Cost and Health Insurance

The average cost of a PSA test is $20 to $50, though you may be required to pay a physician visit fee if you will receive your results at your doctor's office. Medicare covers PSA testing, as do many private health care insurers.

What to Bring

You will want to bring your insurance card to your blood draw. If you are seeing a new physician or one who does not have your previous PSA test results, requesting a copy of your prior records is recommended.

During and After the Test

A laboratory technician or nurse will draw your PSA after receiving an order from your physician.

When you are in the lab or exam room, the technician will cleanse your arm with an antiseptic and perform a venipuncture (blood draw). After taking the sample, she will hold pressure on the site for a few moments and then cover the site with a bandage.

If you notice any bleeding or bruising, applying light pressure for several minutes is all that is usually needed. There are no restrictions following the blood draw, though it's usually advised to keep the site clean and covered for a day or two.

Interpreting Results

The time until your results are available can vary, but they are usually returned within a few days. Your doctor may call you with the results or ask you to come to the clinic to discuss your labs. Interpreting the results of a PSA test can be challenging, and the meaning of a particular number has changed over time.

Reference Ranges

PSA is recorded as nanograms per milliliter (ng/mL) of blood. Most often, a PSA lower than the upper limit of normal means that cancer is not present (though there are exceptions.

Reference ranges can vary depending on the particular lab used, and some ranges are differ based on race as well. The reference for the PSA upper limit of normal used by the Mayo Clinic is as follows:

  • Age less than 40: Less than or equal or 2.0 ng/mL
  • Age 40 to 49: Less than or equal to 2.5 ng/mL
  • Age 50 to 50: Less than or equal to 3.5 ng/mL
  • Age 60 to 60: Less than or equal to 4.5 ng/mL
  • Age 70 to 79: Less than or equal to 6.5 ng/mL
  • Age 80 and over: Less than or equal to 7.2 ng/mL

In general, the higher the PSA (over 4 ng/mL) the greater the risk that cancer is present. But levels can be significantly higher than 4 ng/mL and not be cancer, or the number may be less than 4 ng/mL even if cancer is present. Each man's results must be evaluated individually to determine if further testing is needed (other than a digital rectal exam).

The higher the level of PSA, the less likely that a result is a false positive. For men who have a biopsy for a PSA level between 4 nanograms per microliter (ng/mL) and 10 ng/mL, only one in four will be found to have prostate cancer. When a PSA is greater than 10 ng/mL, around 43 percent to 65 percent of men will have cancer.

Follow-Up

If your PSA is clearly "normal," your doctor will talk to you about when the test should next be performed (guidelines vary and are changing).

If your result is abnormal, the first step is often to repeat the test. Lab errors are not uncommon. It's also important to rule out any factors aside from cancer that could be causing an increase in PSA, such as prostatitis or BPH.

The next step is to determine if further testing is indicated or if it would be better to simply repeat a PSA at a later time. A PSA of 10 or over often means that further testing is needed. But again, this needs to be individualized to determine if the risks of further testing will outweigh any benefits of finding and treating the disease.

A PSA of 4 ng/mL to 10 ng/mL is the "grey zone" and further workup needs to be carefully discussed in light of risk factors, age, general health, any symptoms, personal preferences, and more. The change in PSA over time must also be considered and is sometimes more important than that absolute number of the PSA. Men may also wish to consider other variations of the PSA, such as free PSA when making decisions (see Similar Tests above). Pro-PSA is usually ordered after a PSA result between 4 and 10 is returned.

If it's determined that further workup is needed (keep in mind that a PSA test with or without a digital rectal exam cannot diagnose prostate cancer), tests to diagnose prostate cancer or rule out the disease may include:

  • Transrectal ultrasound: An ultrasound done via the rectum can look for any abnormalities in the prostate, but cannot diagnose prostate cancer unless combined with a biopsy.
  • Multiparametric MRI (mp-MRI) with targeted biopsies of any abnormal regions
  • MRI fusion biopsy (MRI plus transrectal ultrasound) with targeted biopsy of any abnormal regions
  • Ultrasound-guided random 12-core biopsy

Even with biopsies, prostate cancer can sometimes be missed. For men over the age of 50 who have a PSA that is persistently elevated but negative biopsies, a PCA3 RNA test might be considered.

Note that, after treatment, the goal is often to have a PSA of 0. Even small increases may be a call for concern.

A Word From Verywell

The current controversy and debate surrounding the PSA test can leave men feeling somewhat confused about whether or not they should have the test, and what their next steps should be if their results are abnormal. While the possibility of overdiagnosis and overtreatment is there, we know that prostate cancer remains a significant cause of death in men—and that the PSA test can help catch it early. We still do not know if early detection in this fashion reduces the risk of death, but studies at the present time suggest that it does.

Controversies such as this abound in medicine, and it's more important than ever for people to educate themselves and be their own advocates. Ask a lot of questions. This is especially important if you are in a high-risk group (black men and those who have a family history of the disease, for example). If your PSA levels are increasing or elevated, or if variations on PSA testing are abnormal, but your doctor doesn't appear to understand your concerns, consider switching physicians or get a second opinion.

There are also widely varying opinions on the best tests to officially diagnose the disease, as well as the best treatments. If you are not ordinarily assertive in your health care, keep in mind that persistence can sometimes save lives.

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