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Last updated August 2, 2019. 6 minute read

Prostate-specific antigen (PSA) test—its value and limitations

The PSA test has undoubtedly increased the number of prostate cancer cases that are diagnosed each year, especially cases in which the cancer is in its earlier and more treatable stages. And while this might sound like a good thing, it has actually created a whole new set of problems.

Dr Chimene Richa Md Written by Dr. Chimene Richa, MD
Reviewed by Dr. Tzvi Doron, DO

The prostate-specific antigen or PSA test is mainly used to screen for prostate cancer. The purpose of the screening test is to catch prostate cancer before it can spread beyond the prostate gland itself. Once it spreads, prostate cancer can cause a host of symptoms and, ultimately, death. But it’s important to remember that, while prostate cancer is common with 11% of men in the United States receiving a diagnosis during their lifetime, the overall lifetime risk of dying from it is only about 2.5% (USPSTF, 2018). 

Healthcare providers use the PSA test to check the levels of a specific antigen (protein) that is made by normal cells in the prostate gland. In prostate cancer, levels of this antigen in the blood can be outside of the normal range. However, these levels can be high in other benign (non-cancerous) diseases too, especially prostatitis and benign prostatic hyperplasia (BPH). 

You should discuss your risk of different prostate conditions with your healthcare provider, so together you can decide if the PSA test is right for you.

Vitals

  • Prostate-specific antigen (PSA) testing is used to screen for prostate cancer.
  • There is no “normal” blood level of PSA, as the values can change over time.
  • Men with levels of 4-10ng/mL (nanograms per milliliter) have a 25% risk of having prostate cancer.
  • Men with levels higher than 10ng/mL have a 50% or higher risk of having prostate cancer.
  • Benign prostatic hyperplasia (BPH) and prostatitis are common non-cancerous conditions that can cause higher PSA levels.

The PSA test

The PSA test is non-invasive and requires a healthcare provider taking some blood. After your blood is drawn, results typically take about two weeks to come back and usually reported as nanograms of PSA per milliliter of blood (ng/mL). 

An abnormal PSA test may lead to a prostate biopsy. A biopsy is when a small sample of tissue is taken and looked at under the microscope for cancer cells. The presence of cancer cells is what gives the definitive diagnosis of prostate cancer, not a high PSA level. A more elevated PSA is merely an indication that something is not right with the prostate gland and may lead to further testing.

As we’ll see in a moment, there are both risks and benefits to the PSA test. You should discuss any findings with your healthcare provider before deciding whether to undergo screening for prostate cancer.

PSA levels and what they mean

What is a normal PSA level? What happens when it is “abnormal”? There is no easy answer to either question, which is why there is so much discussion about the risks and benefits of prostate cancer screening.

There is no “normal” PSA level as the numbers can vary in the same person throughout their life. On the whole, the risk of prostate cancer goes up with higher measured levels of PSA. But keep in mind that prostate cancer is not the only disease that can make the PSA measure higher than average. Let us go into a little more detail about PSA levels.

Men with very low PSA levels (<0.5–1 ng/ml) have almost no chance of having prostate cancer at the time of testing and a very low risk of advanced prostate cancer for the next 25 years (Bratt, 2015). On the other hand, almost all men with very high PSA levels (more than 50 ng/ml) have advanced prostate cancer unless they have a urinary infection at the time of testing.

What is the best course of action with PSA values in the middle? Well, this is a gray area, and there are no hard and fast rules. In the past, the cutoff for “normal” was considered a PSA of 4.0ng/mL as most people with prostate cancer will have levels above this number. However, studies have shown that 15% of men with PSA levels <4.0ng/mL could still have prostate cancer. Men with PSA levels from 4-10ng/mL have a 25% chance of having prostate cancer. If the PSA is over 10ng/mL, there is over a 50% chance that cancer is present (ACS, 2019).

PSA levels Prostate CA risk
Very low (<0.5-1ng/mL) Almost none
Low (<4ng/mL) 15%
Medium (4-10ng/mL) 25%
High (>10ng/mL) 50% or higher

The PSA test has undoubtedly increased the number of prostate cancer cases that are diagnosed each year, especially cases in which the cancer is in its earlier and more treatable stages. And while this might sound like a good thing, it has actually created a whole new set of problems.

While prostate cancer is the second most common cause of cancer death among American men, the overall chance of dying from the disease is just 2.5% and the five-year survival rate (that chance that someone with this condition will be alive in 5 years) for early-stage prostate cancer is nearly 100% (Fenton, 2018).

These statistics haven’t changed much with the increased use of the PSA test.  So more men are being diagnosed, but their lifetime risk of dying from prostate cancer hasn’t changed. Most men who are diagnosed with this disease will die of causes other than prostate cancer (Fenton, 2018). Finding tumors that are not, and may never be life-threatening, is referred to “overdiagnosis” and treatment of such tumors is “overtreatment.”

Prostate cancer is not the only condition that can cause abnormal PSA test levels. Other common conditions, such as prostatitis and benign prostatic hyperplasia, can do the same thing. An elevated PSA test without any evidence of prostate cancer is called a “false positive” result. Seventy-five percent of men with a moderate (4-10ng/mL) PSA level did not have prostate cancer on prostate biopsy (Barry, 2001). A “false negative” occurs when someone with low PSA levels ends up having prostate cancer. As you can see, prostate cancer screening is not without its risks.

The U.S. Preventive Services Task Force (USPSTF) and the American Urological Association (AUA) recommend against the screening of men of all ages with the PSA test. They found that the drawbacks of PSA screening include pain, fever, bleeding, infection, and temporary urinary difficulties associated with prostate biopsy (Fenton, 2018).

Also, men can suffer psychological harm from false-positive test results. The PSA test cannot distinguish between tumors that will remain inactive and those that will spread to other parts of the body. So men with cancers that are picked up on screening, but never would have caused them any problems, would suffer the consequences (Fenton, 2018).

Here are the AUA screening guidelines (Detection, 2018):

Age Screening recommendation
Men aged <40 years No screening recommended
Men aged 40-54 years Screening is individualized depending on risk factors for prostate cancer (e.g., family history, African American)
Men aged 55-69 years Use shared decision-making with their healthcare provider to decide whether to screen
Men aged 70 years and over No screening recommended

What happens if the PSA test is elevated during prostate cancer screening? According to the National Cancer Institute, if a man, with no symptoms, is found to have a high PSA level, the healthcare provider may check another PSA test to confirm the results (NCI, 2017). If the PSA level is still elevated, the man may need to have PSA tests regularly, looking for any changes over time. 

However, if his PSA level continues to rise or if a suspicious lump is detected during a digital rectal exam (DRE), the healthcare provider may order additional tests, such as a urine test to check for a urinary tract infection (UTI), or imaging tests, such as a transrectal ultrasound, x-rays, or cystoscopy. If these results point to potential prostate cancer, the healthcare provider will refer the patient to a urologist for a prostate biopsy. (6)

Prostate exam

In the past, prostate screening was performed using a digital rectal exam (DRE) and the PSA test together. The DRE allows the healthcare provider to physically examine the prostate to look for lumps or enlargement. However, studies (Mistry, 2003) have shown that the DRE is not a useful exam tool for prostate screenings, and it is no longer recommended for that purpose. The PSA test, while not perfect, is better at detecting prostate cancer in men. However, as it is not without its risks, each man should discuss with his healthcare provider whether or not to have prostate screening done.

Learn more about the prostate exam here.

Non-cancer causes of high PSA levels

One of the drawbacks with using the PSA test for prostate cancer screening is that elevated PSA levels can be caused by factors that are not related to cancer sat all (Barry, 2001). These include:

  • Benign prostatic hyperplasia (BPH), a benign enlargement of the prostate that occurs in older men
  • Age 
  • Prostatitis, infection or inflammation of the prostate gland
  • Ejaculation may affect PSA levels
  • Long-distance bicycle riding (Mejak, 2013)
  • Trauma to the urethra or prostate
  • Urologic procedures, such as a prostate biopsy or cystoscopy

Learn more about the prostate exam here.

In conclusion

Prostate cancer screening using the PSA test remains a somewhat controversial issue in prostate health. There is no “one-size-fits-all” answer to PSA testing. Screening is an individual issue, and it is essential to discuss the risks and benefits with your healthcare provider.