PSA

PSA is measured to help detect prostate cancer, and also to monitor the response to treatment in those with prostate cancer.

Using the PSA test to screen healthy men for prostate cancer is somewhat controversial and is not recommended at present in Australia. This is because in many cases PSA testing detects early cancers that are extremely slow-growing and may never cause life-threatening disease - this may cause further unnecessary testing and treatment. However, men who have an increased risk for prostate cancer (such as Afro-Carribean or African-American men, and those with a family history of the disease) may wish to be screened for prostate cancer.

Two other PSA tests are sometimes requested; free PSA and bound PSA. These tests are not widely used in Australia and their clinical value remains under investergation. Free PSA is sometimes requested when total PSA levels are only mildly elevated to try to differentiate between prostate cancer and other non-cancerous conditions such as BPH. It might also be requested in combination with other tests, such as the rectal examination or biopsy, to confirm a diagnosis of prostate cancer. Once the diagnosis is made, the PSA test might also be used to help your doctor learn about how you are responding to treatment.

The 'normal' value for total PSA are age dependent but total PSA levels greater than 10.0 ng/mL may indicate a high probability of prostate cancer. Levels between 4.0 ng/mL and 10.0 ng/mL may indicate BPH, a non-cancerous swelling of the prostate, or prostate cancer. BHP occurs most frequently in elderly men. Increased total PSA levels may also indicate a condition called prostatitis, which is caused by an infection.

There is some evidence that the free PSA ratio (the percent of total PSA not bound to proteins) can help predict the probability of cancer, especially in patients with total PSA levels in the 'grey-area- range of 4.0 to 10.0 ng/mL. This test may also be useful in early diagnosis of disease when values are between 2.5 and 4.0 ng/mL. A free-PSA test result above 25% is thought to suggest a lower risk of cancer, whereas a lower percentage suggests a higher probability of disease. This ratio may help reduce the number of unnecessary biopsies. A recent study also suggests that very low ratios of free PSA to total PSA (less than 14%) might be associated with a more aggressive form of the disease. Additional studies are ongoing.

In most cases, test results are reported as numbers rather than as 'high' or 'low', 'positive' or 'negative', or 'normal'. In order for the doctor to properly understand laboratory results it is necessary for them to know what the reference range is for a particular test. However, reference ranges can be influenced by the patient's age and sex and, amongst other things, by what drugs they are receiving, the time of day and what they have eaten. Reference ranges can also influenced by the test method and instrument used by laboratory. To learn more about reference ranges, please read the article, Reference ranges and what they mean.

Prostate biopsy or operations on the prostate will significantly elevate PSA levels. The blood test should be done before surgery or six weeks after.

Ejaculation and vigorous physical activity affecting the prostate, such as bicycle riding, may cause a temporary rise in PSA levels. It is also thought that a rectal examination prior to PSA testing might temporarily raise PSA levels but recent studies have not shown this to be true. Excessive doses of some chemotherapeutic drugs, such as cyclophosphamide and methotrexate, may increase or decrease PSA levels.