PSA Test (PSA Levels): Prostate specific antigen
December 5, 2009 by Prostate Dr.
When a man complains of prostate health symptoms, the first procedure that should be done is a DRE (Digital Rectal Exam). And only if the DRE indicates possible presence of BPH/Prostate Cancer will a PSA test be done.
After you have filled out the many forms and paperwork, a blood sample will be drawn for a prostate specific antigen (PSA) test. The doctor may also ask that a prostate acid phosphatase (PAP) test be done from the same blood draw. Some doctors prefer to draw the blood first, since rough palpations of the prostate gland can cause an increase in PSA levels.
DRE suspicious and PSA test levels above normal, the next procedure may be a biopsy of the prostate. If the results still don't provide with a clear image of the case, several other tests may be ordered: a bone scan (in case prostate cancer has metastasized), a magnetic resonance imaging (MRI) test, a computerized tomography (CT) scan, a transrectal ultrasound test (TRUS), a ploidy test, a laparoscopic test of lymph nodes, a prostascint test, reverse transcriptase polymerase chain reaction (RT-PCR) test and several others.
With enough information at hand, the doctor can assign a clinical stage. The stage will most likely influence the treatment decision.
With the increased awareness in prostate cancer, there are newer methods to detect it and one of them is Prostate Specific Antigen test. PSA is a protein enzyme that is normally produced by prostate cells. The presence of PSA in the blood stream is normal, and it can be found in high concentrations in the semen.
It's main purpose is to help liquefy the semen after it has been ejaculated. This liquefaction makes it easier for the sperm to swim in their search for an ovum.
PSA was first used in 1979 to try to identify rapists. Besides being found in the semen, small amounts of PSA is also found in the blood stream. In the mid 1980s it was found that prostate cancer cells also manufacture PSA. Most cancer cells do nothing at all except multiply and expand. The PSA manufactured by these cells is later released into the blood stream and can be measured, considering that the amount of PSA in the blood correlates very closely with the amount of prostate cancer.
The PSA test levels can be used to monitor the progress of the cancer. PSA amount going up indicates that the cancer is actively spreading and growing. However, remember that in cancer there are many exceptions: some prostate cancers become so poorly differentiated that they no longer make PSA. And as a consequence, some men can have metastatic cancer with a very low PSA. But as a general rule, when PSA doubles, then we can be fairly certain that the number of cancer cells have doubled .
This can be a matter of months of weeks. The faster the PSA doubling time, the faster the cancer is growing, so it is very important to have a PSA test done in order to later use it as a starting point.
Significance of PSA test level
Initially, when first discovered, no one knew what "normal" PSA levels were and what high PSA test results were.After statistical evaluations on thousands of men, it was established that the normal PSA should be between 0-4 nanograms per milliliter (ng/ml) of blood . (a nanogram is a billionth of a gram).
What exceptions are there:
all of us are different. What is normal for one man may not be for another. Some men have had significant cancer with a very low PSA. Conversely, a man may have a PSA as high as 12 ng/ml or more simply because of BPH or a prostatic infection.
Studies have shown that PSA can be age specific and the 4 ng/ml is not necessarily a good cutoff point for every one. 4 ng/ml may be considered normal for some younger patients, but many significant cancers may be overlooked in older cases. In older men if 4 ng/ml is considered to indicate cancer, then many of them may undergo unnecessary biopsies or even have an unnecessary radical prostatectomy.
Dr. Joseph E. Oesterling, Editor-in-Chief of Urology, and several other doctors have recommended the following for the age specific PSA test levels cutoff:
-ages 40-49 = 2.5 ng/ml,
-ages 50-59 = 3.5 ng/ml,
-ages 60-70 = 4.5 ng/ml,
-ages 70-75 = 6.5 ng/ml.
Any PSA greater than that listed for the age should be considered suspicious.
Black people are at a much higher risk for prostate cancer and it is usually more aggressive when detected. Studies show that the age specific PSA levels should be much lower for blacks. But again and again, there are no absolute rules in cancer so these figures are only guidelines.
PSA vs. DRE
Each one has it's place in the prostate cancer detection process. Drs. Brawer and Lange (The Journal of Urology, September 1993, page 896) investigated a series of 1,249 cancer patients. The prostate cancer was not detected by DRE in 37.5% (468 men) but was detected by the PSA levels.
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