What is being tested?
This test measures the amount of prostate specific antigen (PSA) in the blood. It was developed as a tumor marker to screen for and to monitor prostate cancer. It is a good tool, but not a perfect one. Elevated levels of PSA are associated with prostate cancer, but they may also be seen with prostatitis (inflammation of the prostate) and benign prostatic hyperplasia (BPH). Mild to moderately increased concentrations of PSA may be seen in those of African American heritage, and levels tend to increase in all men as they age.

PSA is a protein produced primarily by cells in the prostate, a small gland that encircles the urethra in males and produces a fluid that makes up part of semen. Most of the PSA that the prostate produces is released into this fluid, but small amounts of it are also released into the bloodstream. PSA exists in two forms in the blood: free (not bound) and complexed (bound to a protein). The most frequently measured PSA test is the total PSA, which measures the sum of the free PSA and the cPSA (PSA complexed with other plasma proteins). When a doctor orders a “PSA test,” he is referring to a total PSA.

Free PSA and cPSA tests can also be ordered individually. The tests that measure them were developed to better differentiate between cancer-related and non-cancer-related PSA increases. Both of the tests operate on the principle that patients with prostate cancer frequently have altered ratios of the two forms of PSA - decreased amounts of free PSA and increased amounts of cPSA.

PSA is not diagnostic of cancer. The gold standard for identifying prostate cancer is still the prostate biopsy, collecting small samples of prostate tissue and identifying abnormal cells under the microscope. The total PSA test and digital rectal exam (DRE) are used together to help determine the need for a prostate biopsy. The goal of testing is to minimize unnecessary biopsies and to detect clinically significant prostate cancer while it is still confined to the prostate. The term clinically significant is important because while prostate cancer becomes relatively common in men as they age, many of the cases are very slow-growing. Doctors must try to both detect prostate cancer and to differentiate between slow-growing cases and prostate cancers that may grow aggressively and metastasize (spread to other parts of the body). Over-diagnosing and over-treatment are issues with which doctors are currently grappling. In some cases, the treatment can be worse than the cancer, with the potential for causing significant side effects, such as impotence and incontinence. The PSA test and DRE can detect most cases of prostate cancer, but they cannot, in general, predict the course of a patient’s disease.

How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm. The sample should be collected prior to the physician performing a digital rectal exam (DRE) and prior to (or several weeks after) a prostate biopsy.