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Metro Urology
What is the PSA Test?
The PSA (Prostate-Specific Antigen) test is a simple blood test drawn from the arm that reports the level of PSA detected in the blood. PSA is a tumor marker currently used for the early detection, or screening, of prostate cancer. PSA is a protein produced only by the prostate gland, where it is present in high amounts. It is found in lesser amounts in the blood. In general, the higher a PSA level, the greater the risk that a man has prostate cancer. This is complicated by the fact that other non cancerous conditions, such as enlargement (BPH) or prostate infection which also causes higher PSA levels.
PSA Screening is Controversial
Since PSA screening has become popular, the death rate from prostate cancer has decreased. However, it is unclear if this is because of PSA testing, better treatments, or other factors. Also, it is true that when prostate cancer is found earlier with PSA screening, it is more easily and successfully treated. On the other hand, prostate cancer is usually slow growing and may not have been a real threat to a man's life in the first place.
PSA Levels Alone Do Not Prove There Is Prostate Cancer
Only about 20-25% of men with high PSA levels will be found to have prostate cancer on a subsequent biopsy. Non-cancerous conditions such as BPH or prostate infection can also elevate PSA levels. High PSA levels only arouse suspicion for prostate cancer, and a prostate biopsy is necessary to diagnose cancer.
Who Should Have PSA Screening
PSA screening is usually recommended for men who are at risk of having prostate cancer impair or shorten their lives. According to the AUA (American Urological Association) and ACS (American Cancer Society), men are encouraged to have annual PSA screening at age 50 and older, especially if there is a 5-10 year life expectancy. They recommend screening higher risk men (blacks, strong family history of prostate cancer) at age 40 or 45. Other medical groups caution against routine PSA screening, and recommend it only on an individual basis.
What Is the Cut-off Level for PSA?
Traditionally, a level of 4.0 ng/ml has been considered a normal PSA screening test. However, there is good evidence that many prostate cancers may be missed using this level for all men. Currently, there is controversy over what is the best PSA cut-off. If the level is set too low, unnecessary biopsies may be done leading to the diagnosis and treatment for prostate cancer that may never have threatened a man's life. However, if the level is too high, serious cancers may be missed.
Research Is Being Done to Improve PSA Screening
Although these are still controversial, some of the more common methods to attempt to make screening with PSA more accurate include:
- PSA velocity measures the rate of change of PSA over time, since a faster rise in PSA raises the possibility of a potentially serious prostate cancer.
- Free PSA testing recognizes there are two forms of PSA circulating in the blood, both free (unattached to protein) or bound (attached to protein). With prostate cancer, there is often less free PSA than seen in those other benign conditions known to cause an elevated PSA.
- Age-adjusted PSA levels utilize the fact that a man's PSA level gradually rises as the prostate naturally slowly enlarges with age (BPH). In other words, it is expected that younger men should have a lower PSA, and older men a higher PSA. Instead of a universal cut-off of 4.0 ng/ml being used for all men, the following are typical age-adjusted values:
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Age 40-49 |
PSA level 2.5 |
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50-59 |
3.5 |
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60-69 |
4.5 |
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70-79 |
6.5 |
PSA Screening Needs Careful Thought
PSA screening, while easy, does have limitations, and thus men and their doctors need to weigh the pros and cons of this test. Because of the complexities surrounding PSA screening, it is recommended that a physician experienced in prostate cancer and PSA testing helps you decide on screening, interpretation and follow-up of PSA results.
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