Prostate-specific antigen (PSA) is mostly found in semen, which also is produced in the prostate. Small amounts of PSA ordinarily circulate in the blood. PSA levels increase when you have an enlarged prostate. Higher PSA levels can also be due to recent procedures, infection, surgery or prostate cancer. If the PSA test returns abnormally high, it is important to perform additional tests to rule out the presence of cancer cells.
The limitations of PSA testing include:
PSA-raising factors. Besides cancer, other conditions that can raise PSA levels include an enlarged prostate (benign prostatic hyperplasia, or BPH) and an inflamed or infected prostate (prostatitis). Also, PSA levels normally increase with age.
PSA-lowering factors. Certain drugs used to treat BPH or urinary conditions, and large doses of certain chemotherapy medications, may lower PSA levels. Obesity can also lower PSA levels.
Misleading results. The test doesn't always provide an accurate result. An elevated PSA level doesn't necessarily mean you have cancer. And many men diagnosed with prostate cancer have a normal PSA level.
Over diagnosis. Studies have estimated that between 23 and 42 percent of men with prostate cancer detected by PSA tests have tumors that wouldn't result in symptoms during their lifetimes. These symptom-free tumors are considered over diagnoses — identification of cancer not likely to cause poor health or to present a risk to the man's life.
The potential risks of the PSA test are essentially related to the choices you make based on the test results, such as the decision to undergo further testing and treatment for prostate cancer. The risks include:
Biopsy issues. A biopsy is a procedure that carries its own risks, including pain, bleeding and infection.
Psychological effects. False-positive test results — high PSA levels but no cancer found with biopsy — can cause anxiety or distress. If you are diagnosed with prostate cancer, but it appears to be a slow-growing tumor that doesn't result in illness, you may experience significant anxiety just knowing it's there.
What you can expect
A nurse or medical technician will use a needle to draw blood from a vein, most likely in your arm. The blood sample is then analyzed in the lab to measure your PSA level.
Results of PSA tests are reported as nanograms of PSA per milliliter of blood (ng/mL). There's no specific cutoff point between a normal and abnormal PSA level. Your doctor might recommend a prostate biopsy based on results of your PSA test.