What Is a PSA Test for Prostate Cancer?

Elevated levels of PSA (prostate-specific antigen) in the blood can indicate prostate cancer, among other conditions. PSA tests can be administered both as a screening tool, to detect elevated risk of prostate cancer, and as a tool to evaluate the effectiveness of prostate cancer treatment. There is some disagreement among the medical community as to when prostate cancer tests should be used for screening; however, there is a some consensus on interpreting results of PSA tests and their relationship to prostate cancer.

When a PSA Test Is Used

• PSA tests may be used alone, or in conjunction with digital rectal exams (DRE), to screen for prostate cancer. An abnormal result on a PSA or DRE can indicate the need for further testing to rule out prostate cancer. PSA tests are also used to monitor how effective treatment is for men who have prostate cancer, or to monitor the advancement of slow growing prostate cancer in men who are not currently undergoing treatment for the cancer. Finally, regular PSA tests may be recommended for men who have previously had prostate cancer, to monitor for the possibility of recurrence.

Who Should Have a PSA Test

• Medical experts disagree on whether PSAs should be administered as part of routine checkups to screen for prostate cancer. The National Cancer Institute and Center for Disease Control do not recommend regular screening for prostate cancer using the PSA test, as of 2009. However, the American Cancer Society recommends an annual PSA test for males over the age of 50 (or for higher risk males, including men of African descent and men with a family history of cancer beginning at age 45). When men exhibit symptoms that could potentially be caused by prostate cancer, such as painful urination or back and pelvic pain, a PSA is usually recommended in conjunction with other tests, to rule out prostate cancer as a cause of these symptoms. Men undergoing treatment for prostate cancer, or who have recovered from prostate cancer, may also be advised by their physician to have routine PSA tests.

Interpreting the Test Results

• Although there is some disagreement about the exact interpretation of PSA test results, Lab Tests Online states that the normal value of PSA is 4.0 nanograms per milliliter of blood; however Lab Tests Online cautions that some believe the level should be lowered to 2.5 nanograms per milliliter of blood in order to diagnose more cases of prostate cancer early on. Lab Tests Online suggests that there is a consensus in the medical community that a PSA level greater than 10 nanograms per milliliter of blood indicates a greater than 67 percent increased risk of prostate cancer. Levels between 4.0 and 10 nanograms per milliliter indicate a 25 percent increased risk of prostate cancer. However, levels within this range are considered to be unclear and an additional test called a "free PSA" test may be recommended to determine whether the elevated levels of PSA are "free PSA." A higher ratio of free PSA indicates a lower risk of prostate cancer, while a lower level of free PSA indicates a higher risk. Doctors may also look at the change in PSA concentrations over time. Significant continued elevation of PSA levels over a period of three or more years indicates that prostate cancer is likely. PSA velocity and density may also help doctors to interpret the results of the PSA test.

Causes of Elevated PSA Levels

• A digital rectal exam can cause PSA levels to rise, so when the tests are performed together, the DRE should always be performed last. A biopsy will also raise PSA levels, so a PSA test should be performed prior to a biopsy. Rigorous exercise, chemotherapy drugs, certain other medications and prostate infections can also raise PSA levels.

PSA and Prostate Cancer

• PSA tests are also administered during prostate cancer treatment to gauge its effectiveness. If treatment is successful, PSA levels should fall and eventually be almost undetectable. If the PSA levels do not fall, the treatment is not successful. Furthermore, some men (especially elderly men) do not undergo treatment for slow growing prostate cancers, but instead choose to "watch and wait." During this time, when the doctor simply monitors the growth of the cancer to ensure that it continues to progress slowly, PSA tests are used routinely to monitor the rate of growth of the cancer.