The prostate-specific antigen (PSA) test is a screening test for prostate cancer. An elevated PSA level can be a sign of prostate cancer or an increased risk of prostate cancer, but other conditions can also raise PSA levels. Here is what you need to know about the PSA blood test.
Prostate cancer is a very common cancer that affects men. Prostate cancer screening is important for the early identification and treatment of prostate cancer.
Prostate-specific antigen (PSA) is a protein made by the prostate gland. Elevated blood levels of PSA are associated with an increased risk of prostate cancer.
Prostate cancer can sometimes raise blood PSA levels. Other conditions, such as an enlarged prostate (benign prostatic hyperplasia or BPH), can also raise or lower PSA levels.
If you have an abnormal PSA level then additional tests are needed to identify the cause.
The prostate and PSA
The prostate gland is involved in semen production; it surrounds the urethra between the bladder and penis. Prostate-specific antigen (PSA) is a protein that is only made in the prostate and is detectable in the blood. Conditions that cause the prostate to grow can increase PSA levels—these include prostate cancer, an enlarged prostate, and an infected prostate.
Prostate cancer screening
Prostate cancer is the second most common non-skin cancer in the US and the second most common cause of cancer death in men. The American Cancer Society recommends screening for prostate cancer in men who are:
Age of 50 with an average risk of prostate cancer and at least 10-year life expectancy.
Age of 45 who are African American or have a first-degree relative with prostate cancer before age 65.
Age of 40 who have more than one first-degree relative with prostate cancer before age 65.
The two main screening tests for prostate cancer are a digital rectal examination (DRE) and a blood test for PSA levels.
PSA levels give some information about prostate cancer risk. The higher your PSA level, the more likely you are to have prostate cancer. PSA levels are reported in nanograms per milliliter (ng/ml). A PSA level under 4 ng/ml is considered normal and PSA levels between 4 and 10 ng/ml are considered borderline, with a 25% chance of having prostate cancer. Men with PSA levels above 10 ng/ml have a 50% chance of having prostate cancer.
Those statistics may sound frightening, but PSA levels do not tell the whole story. While prostate cancer can be deadly, some common forms of prostate cancer grow so slowly that they will never harm your health if left untreated. A PSA test cannot diagnose cancer nor can it differentiate between different types of prostate cancer. It can, however, help monitor the effectiveness of cancer treatment.
What can raise PSA levels?
Several conditions other than prostate cancer can raise PSA levels. PSA levels normally increase with age, and larger men may have a larger than average prostate. Other causes of elevated PSA levels include:
- Benign prostatic hyperplasia (BPH) – an enlarged prostate
- Prostatitis (prostate infection)
- Urinary tract infection (UTI)
- Stimulation of the prostate from recent sexual activity or a digital rectal exam (DRE)
What can lower PSA levels?
Some conditions and medications can lower PSA levels. This can make a PSA test less accurate. These include:
- Drugs used to treat BPH: finasteride (Proscar, Propecia) and dutasteride (Avodart)
- Some chemotherapy drugs
What if my PSA is high?
First of all, don’t panic. There are many possible reasons for a high PSA level, most of which are not cancer. Even if you do have prostate cancer, the prognosis varies and some types of prostate cancer are so slow growing that they do not need treatment.
If you have increased PSA levels your doctor will need to order additional blood tests to determine what is raising your PSA levels. These tests may include:
- Free-PSA test (unbound PSA)
- PSA velocity (change in PSA level over time)
- PSA density (PSA per volume of tissue - adjusts for prostate size)
You may also need imaging tests, such as magnetic resonance imaging (MRI), to assess your prostate. A digital rectal exam (DRE) is also recommended to detect an enlarged prostate or lumps that may be a sign of cancer. If something is found, a prostate biopsy may be recommended.
Limitations of PSA testing
PSA levels cannot diagnose prostate cancer nor can they differentiate between types of prostate cancer. Only a prostate tissue biopsy can accurately diagnose prostate cancer. Additionally, the PSA test may give a false-positive result, meaning that the test shows high PSA levels when they are normal.
PSA testing can help detect prostate cancer at its early stages, but it can also lead to unnecessary procedures and treatments. High PSA levels with no symptoms of the disease can be caused by very slow-growing cancer that does not require treatment. In that case, prostate biopsy and cancer treatment may cause more harm than good, both physically and psychologically. Prostate cancer treatment can lead to complications such as erectile dysfunction (ED) or bowel and bladder incontinence.
Talk to your doctor
A PSA blood test can detect prostate cancer but it does not paint a complete picture of prostate health. Having a high PSA level doesn't mean that you have prostate cancer and a normal PSA level does not rule out cancer. A PSA test can offer clues that a potentially dangerous condition exists, but elevated PSA levels require additional tests to determine the cause. PSA testing is not recommended for all men. If your doctor does recommend it, discuss the potential risks and benefits of PSA testing with them. Ultimately, you must decide whether a PSA blood test is right for you.