||PSA test results can be interpreted a number of different ways and there may be differences in cutoff values between different laboratories. The normal value for total PSA is considered to be less than 4.0 ng/ml (nanograms per milliliter of blood). There are some that feel that this level should be lowered to 2.5 ng/ml in order to detect more cases of prostate cancer. Others argue that this would exacerbate over-diagnosing and over-treating cancers that are not clinically significant.
There is agreement that men with a total PSA level greater than 10.0 ng/ml are at an increased risk for prostate cancer (more than a 67% chance, according to the ACS). Levels between 4.0 ng/ml and 10.0 ng/ml may indicate prostate cancer (about a 25% chance, according to the ACS), BPH, or prostatitis. These conditions are more common in the elderly, as is a general increase in PSA levels. Concentrations of total PSA between 4.0 ng/ml and 10.0 ng/ml are often referred to as the “gray zone.” It is in this range that the free PSA is the most useful. When men in the gray zone have decreased levels of free PSA, they have a higher probability of prostate cancer; when they have elevated levels of free PSA, the risk is diminished. The ratio of free to total PSA can help the doctor decide whether or not a prostate biopsy should be performed.
When the cPSA test is used as a screening tool, increased levels may indicate an increased risk of prostate cancer, while lower levels indicate a decreased risk.
In addition to the introduction of the free PSA and cPSA tests, there have been efforts to increase the usefulness of the total PSA as a screening tool. While none of these efforts have been widely accepted yet, researchers are studying them and some doctors are utilizing them. They include:
PSA velocity. This is the change in PSA concentrations over time. If the PSA continues to rise significantly over time (such as 3 or more years), then it is more likely that prostate cancer is present. If it climbs rapidly, then the affected person may have a more aggressive form of cancer.
PSA doubling time. This is another version of the PSA velocity. It measures how rapidly the PSA concentration doubles.
PSA density. This is a comparison of the PSA concentration and the volume of the prostate (as measured by ultrasound). Men with larger prostates tend to produce more PSA, so this factor is an adjustment to compensate for the size.
Age-specific PSA ranges. Since PSA levels naturally increase as a man ages, it has been proposed that normal ranges be tailored to a man’s age.
During treatment for prostate cancer, the PSA level should begin to fall. At the end of treatment, it should be at very low or undetectable levels in the blood. If concentrations do not fall to very low levels, then the treatment has not been fully effective. Following treatment, the PSA test is performed at regular intervals to monitor the person for cancer recurrence. Since even tiny increases can be significant, those affected may want to have their monitoring PSA tests done by the same laboratory each time so that testing variation is kept to a minimum.