When we take any test, it is preferable to get a definite answer: "yes, you have the cancer" or "no, you don't". Unfortunately the PSA test is not that good. At best, it is an indicator of the probability or risk that you have prostate cancer. This can be very helpful, because it guides the decision about whether you should have further tests. However it does mean that the interpretation of PSA levels is not necessarily straight forward.
Many Factors Elevate and Lower PSA Results
Most men facing a PSA (prostate-specific antigen) test for prostate cancer may not realize that many factors can influence the result. Nor do doctors always provide patients with a list of things not to do or not to take before the test.
So here’s a partial list of things that affect a diagnostic PSA test, both up and down.
What Elevates the PSA Test
The higher a man’s PSA level, the more likely it is that cancer is present. Here are some factors that elevate a result:
* Age alone can increase PSA levels. The older a man gets, the likelier his PSA will rise, yet it may mean nothing. For instance, a man might have a PSA reading of 5.5 at seventy, and not have cancer; yet that score in a fifty-something would raise concern.
* Sex. Doctors generally recommend men should abstain from sex at least two days prior to testing. Studies show that ejaculation within that period before a PSA test may increase PSA levels in the blood.
* Stimulation of the prostate, such as a prostate massage or a long bike ride, could elevate PSA levels.
* Inflammation of the prostate gland. Prostate problems, such as benign prostatic hyperplasia (BPH) or prostatitis, can inflate PSA levels.
* Infections of the prostate may cause PSA levels to rise. These can produce no symptoms, so patients might not be aware of them.
* A man with a larger than average prostate may have a higher than normal PSA reading, even if this prostate is healthy. (A larger prostate produces more PSA into the blood.)
* Digital rectal exams and biopsies of the prostate may cause PSA levels to rise. It should be noted that an increase in PSA caused by a DRE is not thought to be significant enough to produce a false-positive result. On the other hand, a biopsy may elevate PSA levels for as long as four weeks.
