The PSA Test: What to Expect

The prostate-specific antigen (PSA) test is a blood test that measures your PSA levels and is used to screen for prostate cancer. Men with prostate cancer usually have a higher PSA level and the risk of being diagnosed with prostate cancer generally increases with PSA values.

The PSA test can also be used to monitor the response of patients undergoing treatment for prostate cancer. A rising trend of PSA values denotes disease progression in this setting.

Learn more: Should You Take the PSA Test?

A few factors may affect your PSA results, and could lead to inaccurate interpretations. The following should be avoided up to 48 hours before your PSA test:

• Intensive exercise
• Ejaculation

If you experience a urinary tract infection or have had a prostate biopsy right before your PSA test, your doctor may advise you to take the test another time. You should also keep your doctor informed of all medications and supplements you are taking in case they interfere with your results. While some supplements may help to lower your PSA levels, they may not reduce your risk of prostate cancer and may mask the disease instead.

Your blood will be drawn, and you may feel a slight prick or pinch as the needle is inserted. Wearing tops with sleeves that can be rolled up easily is recommended.

Afterwards, your blood will be sent for analysis to determine your PSA levels.

The definition of significantly abnormal PSA levels has evolved over the years. Generally, while recommendations may vary, the commonly suggested threshold for concern remains at 4 ng/mL.

However, this threshold was derived from early studies. Now, it's been found that PSA usually tends to increase as you age. Still, this may not be indicative of prostate cancer. After these findings, a new consensus was reached, concluding that PSA thresholds should increase with age.

The American Urological Association’s suggested threshold levels are as follows:

Beyond these reference values, it has also been shown that a PSA level of 4–10 ng/mL has an approximately 25% risk of prostate cancer while a PSA level above 10 ng/mL suggests a risk of over 50%.

When it comes to understanding your results however, it’s important to remember that the PSA test alone cannot diagnose prostate cancer. Instead, it helps serve as an early triage to trigger further assessment of the prostate by your doctor, who can then decide if further tests are needed.

If your doctor notes that you have a higher PSA than expected, you will likely be asked to repeat the PSA test, before continuing on to additional investigations. The reason for this is that there is a 25–40% chance of unexpectedly high PSA levels returning to normal after retesting.

If you do have an abnormally high PSA result, there may not be a need to panic just yet. PSA as a tumor marker can be imperfect, especially as many other benign conditions of the prostate can also result in an increased PSA level. A few of these include:

• Prostate inflammation
• Benign prostate hyperplasia
• Ejaculation
• Urinary retention
• Age
• Race (e.g. Black men in the US tend to have higher PSA levels than White men)

As such, your doctor may suggest some other less invasive tests, such as a magnetic resonance imaging (MRI) scan or a second biomarker test, to further understand your risk profile before recommending undergoing a biopsy for a definitive diagnosis.

If your PSA results are normal and you do not have any other existing risk factors for prostate cancer, there may not be a need for any further follow-up.

However, if you still have risk factors for an increased risk of prostate cancer (e.g. family history of prostate cancer or the existence of certain mutations that increase your likelihood of having prostate cancer), you may be recommended to continue regular PSA checks as a precautionary measure. These screenings are adjusted based on your health and personal risks and are formulated as part of shared decision-making between you and your doctor.

A suggested guide by the American Cancer Society states that if your PSA level is less than 2.5 ng/mL, you may extend your follow-up screenings to once every two years. If your PSA level is 2.5 ng/mL or higher, you should follow up with yearly screening instead. Additionally, if you are aged 55–69 years old, and your PSA level is over 1 ng/mL, the American Urological Association also suggests screenings every two years, and every four years if it’s below 1 ng/mL.

Finally, while the PSA test is not the be-all and end-all of prostate cancer diagnosis, it serves as an important step in your cancer journey, and can help provide some quantitative reassurance about your cancer risk and guide you on the next best steps to take.