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 The PSA Test: How Does It Work?
Who Should Have It Done?
How Accurate Is It?

For over ten years, medical researchers have known about Prostate Specific Antigen -- PSA -- as a "marker" for prostate cancer.  It has only been in the last several years, however, that testing for this substance in men's blood has been used to help assess a man's risk for the disease. 

According to William J. Catalona, M.D., Washington University School of Medicine, St. Louis, in a report published recently by the Journal of the American Medical Association, "An elevated PSA does not mean the presence of cancer, but rather indicates the presence of prostatic disease and the need for further evaluation. Cancers smaller than 1 cm usually do not elevate PSA levels.  More than 90 percent of cancers detected through PSA-based screening have the potential to become clinically important, judged by their size and grade.  The goal of PSA screening," he stressed, "should be to detect the cancer before the PSA level rises above 10 ng/L."

WHAT IS IT?

PSA is a protein excreted only by the prostate, a gland located at the neck of the bladder that surrounds the urethra, the tube through which urine and sperm exit.  The prostate is one of the male sex glands that works in response to hormones to secrete fluids that help transport sperm during ejaculation.  A healthy prostate is approximately the size of a walnut and weighs about an ounce. 

For most of a man's life, this gland does its job without notice.  Then, somewhere around age 50, the gland suddenly has a growth spurt.  It can become enlarged enough to squeeze the urethra, playing havoc with a man's ability to urinate. 

In most cases, this is caused by a condition called Benign Prostatic Hyperplasia (BPH) rather than cancer.  But, it is during this same time frame when a man's risk for developing prostate cancer begins increasing.  The disease rarely exhibits any symptoms in its early stages so, by the time symptoms do appear, the cancer is likely to have already spread into other parts of the body.

Measuring a man's PSA  level involves a simple blood test.  Generally, the higher the level of PSA in the blood, the more likely it is that prostate cancer will be found.  Cancerous prostate tissue secretes about 10 times as much PSA as normal tissue does.  It is measured in nanograms -- billionths of a gram -- per milliliter of blood. Levels below 4 ng/mL are considered the upper range of normal.  (If the test turns up more than 10 ng/mL, there is a 67 percent chance that the man has prostate cancer.)

There are several things other than cancer that can drive the levels up: prostate enlargement, some medications, infection, or a recent biopsy.  Despite earlier warnings, a digital exam does not provoke additional secretion of the protein. The drug finasteride (ProscarTM )  -- prescribed for an enlarged prostate -- can also skew a PSA test by reducing the level.

The change in PSA levels has also turned out to be an important diagnostic tool to detect the new -- curable -- prostate cancers.  Tracking year-to-year changes in the PSA level can alert the physician that additional tests may be appropriate.

HOW ACCURATE IS IT?

As pointed out earlier, no single test is absolutely fail-safe in the detection of prostate cancer.  In recent studies, one fourth of men with mild PSA level elevations (4 to 10 ng/mL) were found to have cancer, although it sometimes took 2, 3 or even 4 biopsy sessions to diagnose the cancer through a biopsy; most of them were confined to the prostate.  The other three quarters were false-positive results.  There were also some false-negative cases -- men with cancer that did not elevate the PSA.

Rates of false-positive PSA screening test results increase with age since about 10 to 12 percent of all men over the age of 50 have elevated PSA levels.  The test also fails to detect 20 to 40 percent of the smaller cancers that occur near the rectal surface of the prostate and can be detected by DRE.

WHO SHOULD HAVE THE PSA TEST?

While the results of a number of studies to determine the overall value of prostate cancer screening are still years away, the American Cancer Society and the American Urological Association now recommend PSA testing -- along with a digital rectal exam -- beginning at age 50, and at age 40 for men in the high risk categories and those with a strong family history of the disease.

Preliminary studies -- reported in both the New England Journal of Medicine and the Journal of the American Medical Association -- found that measuring PSA levels, when done along with a DRE, increases the chances of detecting PC by about 70 percent, compared to using the DRE alone, and more than doubles the percentage of cancers that are confined to the prostate at the time of diagnosis.

 

   

 

Olivamine


Houston Real Estate

 

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ProstateAction.com is NOT a medical website. It was developed to provide what we hope will be useful information for men who have been diagnosed with prostate disease…and their family members. We do NOT have doctors to answer your questions, we do NOT make medical referrals or offer second opinions, and we will not reply to questions about any specific case. Instead, we hope that you will use our LINKS section to locate other sites of interest; utilize our message boards to discover prostate cancer screenings and related events; and to use the Forum area to “discuss” prostate cancer issues with others who share your interests and concerns. We reserve the right to delete any objectionable postings.

The health and medical information on the World Wide Web comes from many sources and changes daily. There are likely to be errors and omissions in this information. This web site, its contributors nor its sponsors represents or warrants that the information in this Web Site or accessed through this Web Site is accurate or complete.

Please direct your medical and health questions to your health care provider.

It is our objective to promote an exchange of information about prostate health. We do not endorse or recommend specific medical treatments, but we encourage visitors to our site to explore a variety of points of view.

 

 

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