Prostate-Specific Antigen Blood Test (PSA Test)

What Is It?

The prostate-specific antigen blood test (PSA test) is a screening test that measures the amount of a chemical called prostate-specific antigen (PSA) in a man's blood. PSA is a chemical made by the prostate, a sex gland located near a man's bladder that makes the fluid in semen. PSA levels normally increase as a man ages, but a higher-than-normal PSA level can mean that cancer has developed in the prostate gland. However, high levels of PSA also can be found in other conditions that are noncancerous, including prostatitis (inflammation of the prostate) and benign prostatic hyperplasia, an enlargement of the prostate that affects many older men.

What It's Used For

PSA is used mainly as a screening test for cancer of the prostate. In men who have been diagnosed with prostate cancer, PSA is measured to determine if the cancer has returned after surgery or whether the cancer is growing or shrinking after treatment with hormones or radiation.

The question of whether to do screening tests for prostate cancer remains controversial. Prostate cancer is the most commonly diagnosed cancer in men in the United States and the second leading cause of cancer death in this group. PSA testing can be used to detect the earliest stage of prostate cancer, before the disease causes any symptoms. Many experts believe that PSA testing is the best way to reduce a man's chance of dying of prostate cancer. This is because the early stages of prostate cancer are much more likely to be curable.

However, other experts fear that if PSA is overused, some men will be diagnosed and treated for cancers that have little potential to cause harm. Many older men develop prostate cancer that never spreads and never causes any problems. Most of these harmless cancers would go undetected if screening was not done. Since treatment for prostate cancer can have serious side effects, screening all men for prostate cancer might end up causing more harm than good. Unfortunately, there is no reliable way to determine in advance which cancers need treatment and which are likely to be harmless.

Studies are being done that will help to settle this controversy. In the meantime, most expert panels that make recommendations about cancer screening do not recommend routine PSA testing for all older men. Instead, they encourage men who are at risk of the disease to make an individual decision about screening, after they have discussed the risks and benefits with their health care professionals.

A man who decides to undergo screening for prostate cancer might think the following:

"The PSA test is the best way to protect myself from prostate cancer. Even if it saves one life, it is worth the uncertainty and all of the possible side effects of treatment. I'm one of those people who just likes to know."

A man who chooses not to be screened might think this way:

"No one is sure if screening really helps, and it may actually lead to unnecessary treatment. I think I'll wait until we know more."

For men who want to be screened for prostate cancer, the PSA test usually is combined with a digital rectal exam. Most experts recommend that screening be done every one to two years, beginning at age 50. Men with an increased risk of prostate cancer may wish to begin screening at age 45. This includes African-American men, who have a 70 percent higher rate of prostate cancer than white men, and men whose father or brother has been diagnosed with prostate cancer.

PSA testing is likely to be less useful in men older than age 75 and men who have serious medical problems or other reasons for a limited life expectancy. This is because it may take a decade or more for prostate cancer to grow from the stage at which it can be first detected to the point where it causes symptoms or harm.

Preparation

Ejaculation can cause your PSA to rise briefly, so you should avoid sexual activity for at least 48 hours before having your PSA level tested. Since blood for your PSA test probably will be taken from your arm, wear a shirt or sweater with sleeves that roll up easily. If you recently have had cystoscopy or needle biopsy of the prostate, let your doctor know so you can schedule your PSA test at another time. Those exams can raise PSA levels for a few weeks, which may make it harder to interpret the result of your PSA test. PSA testing also should not be done until several weeks after you have been treated for a urinary tract infection.

How It's Done

Blood for a PSA test usually is drawn from a vein in the crook of your elbow. The area from which blood will be taken will be cleaned with an alcohol swab, and a sterile needle will be used to draw a few ounces of blood into a tube. The puncture site will be covered with a small gauze or bandage. Your blood sample will be sent to a lab where the PSA level is measured.

Follow-Up

Call your doctor for your PSA test results about one week after your blood has been drawn. If your result is abnormal, your doctor may recommend further blood tests or additional testing, such as a prostate ultrasound or a biopsy of the prostate.

Risks

Having your blood drawn is a simple procedure and there are few, if any, risks. However, when used as a screening test, PSA does have some risks, including:

* A risk that your PSA test will be abnormal and that you will need to undergo further testing, such as a prostate biopsy. Keep in mind that as many as three-quarters of men with an elevated PSA level do not have prostate cancer. However, many men who are told that their PSA test is abnormal will have some anxiety until final results are available.

* A risk that screening will lead to treatment for prostate cancer that may or may not be necessary, but that may cause serious side effects.

* A risk that your PSA level will be normal even if you do have prostate cancer.

Be sure to discuss these risks and the benefits of PSA testing with your doctor before you have your blood drawn.

When To Call A Professional

Call your doctor if blood continues to ooze from the needle puncture site or if the site becomes red, swollen or painful.

Prostate Cancer Gene Test Provides New Early Detection

ScienceDaily (Oct. 17, 2008) — Prostate cancer (PCa) is one of the most common male cancers in the Western world. Currently, early detection of PCa depends on an abnormal digital rectal examination and an elevated prostate-specific-antigen (PSA) level requiring a prostate biopsy, often associated with anxiety, discomfort, complications, and heavy expenses.

The prostate-cancer-gene-3 (PCA3) test is a new PCa gene-based marker carried out with a urine sample. PCA3 is highly specific to PCa and has shown promising early detection results at repeat biopsy. It may allow patients to avoid unnecessary biopsies. The PCA3 gene is dominant in over 95% of malignant prostate tissue compared to benign and normal prostate tissue.

Several studies have been done to evaluate the PCA3 assay. In 2007, Marks et al showed that urine PCA3 levels were more accurate than serum PSA measurements for predicting the results of repeat biopsy (Marks LS, Fradet Y, Deras IL, et al. PCA3 molecular urine assay for prostate cancer in men undergoing repeat biopsy. Urology 2007; 69:532–5).

In the October 2008 issue of European Urology, Haese et al took the study by Marks et al even further in their evaluation of the PCA3 assay in a larger population of European men with one or two negative biopsies scheduled for repeat biopsy in order to determine its effectiveness in detecting PCa at repeat biopsy.

The PCA3 score was calculated and compared to biopsy outcome. The diagnostic accuracy of the PCA3 assay was compared to the percentage of free prostate-specific antigen (%fPSA). Most of the PSA that circulates in the serum is attached to larger protein substances, so called 'complexed' PSA. The rest of the PSA is unbound or 'free'. Research suggests that PSA created by prostate cancer is more likely to be the 'complexed' type while non-cancerous or benign PSA is more the 'free' type.

In 463 men, the positive repeat biopsy rate was 28%. The probability of a positive repeat biopsy increases with rising PCA3 scores. The PCA3 score was superior to %fPSA for predicting repeat prostate biopsy outcome and may be indicative of clinical stage and significance of PCa.

The utility of the PCA3 score is independent of the number of previous biopsies, prostate volume, and total PSA.

PSA - what is it?

PSA or Prostate Specific Antigen is a protein which is secreted into ejaculate fluid by the healthy prostate. One of its functions is to aid sperm movement. Normally, only very low levels of the enzyme are able to enter the blood stream. However, because in cancer the normal structure of the tissue is disrupted, considerably more PSA is able to leak into the blood stream, and for this reason, a raised level of PSA in blood (or serum) can indicate the presence of prostate cancer.

Prostate Cancer - the Psa Test Could Save your Life

What is PSA?

PSA is prostate specific antigen. PSA is a protease (protein) secreted the prostate gland. Its levels in the blood are elevated in men with both benign prostatic hyperplasia and prostate cancer. PSA is now an accepted and routine screening test for prostate cancer.

The PSA Test

PSA presence in the blood is very low, so its detection requires a very sensitive type of technology.

The test uses the monoclonal antibody technique. The PSA protein exists both in the blood by itself, and joined with other substances. By itself, it is free PSA, and joined with other substances, bound PSA.

The term ‘Total PSA’ is the total both forms. The PSA test gives the result of the Total PSA

Results of the PSA Test

The highest normal level of Total PSA is 4 nanograms per milliliter, or ng/mL. Statistics show men’s prostate gland will generally increases in size and produces more PSA with increasing age.

Therefore aging has a great role in the actual results of the test. However, doctors would be concerned with anyone who had a result of over 4.5 ng/mL, and would generally do a biopsy to determine physically if cancer were present

Specific Use of the PSA Test for Cancer

Doctors are using the PSA test now in two ways. First as a screening test to determine elevated PSA levels (which might indicate cancer, but can also indicate other conditions as well), or as a monitor test for those who are known to have prostate cancer.

With the screening technique, any increased levels over 4.5 ng/mL require further investigation. As a monitoring test, high levels of PSA can indicate the growing or reducing threat of cancer.

However an abnormal result also can indicate a recurrence of prostate cancer following therapy.

For example, in men with a surgically removed prostate gland (prostatectomy), where all of the cancer was contained, a PSA test should result in 0. However, if in these men the PSA test is positive or shows increasing levels, it shows the cancer was not successfully removed and / or it has spread.

PSA Also Can Show Non-Cancerous Conditions

The PSA test result can indicate conditions other than cancer.

Often a higher PSA test result indicates benign prostatic hypertrophy, which his enlargement or hyperplasia of the prostate gland. These conditions are due to an increase aging in certain men.

Also infection of the prostate gland, known as prostatitis, will cause an abnormal elevation of PSA.

There are other conditions also which can result in higher levels of PSA that are non-cancerous.

In each case however, the doctor will first perform a biopsy to determine if cancer cells are present.

The Free PSA Test

Free PSA in the blood exists as well as bound PSA, and there is now a test for Free PSA. Studies have shown that levels of free PSA decrease in men with prostate cancer.

The Free PSA levels in men with benign conditions will not decrease. Levels of Free PSA differ from test procedure to test procedure, but in any case, it is a good indication of the presence of cancer if the levels are shown to be decreasing.

Who Should Test for PSA

Any many over 40 years old now should test for PSA. Every man over 50 must test for PSA to insure that if there is a problem, it can be treated early. Consult your physician if this article concerns you.

Other forms of PSA testing

New forms of the PSA blood test make it more accurate in diagnosing prostate cancer. One such test is the ‘free to total’ PSA test. In both healthy men and those with prostate cancer, the prostate specific antigen in the bloodstream latches onto protein. In men with benign prostatic enlargement, the prostate specific antigen tends to be free of protein.

The ‘free to total’ PSA test compares the amount of ‘bound’ to ‘unbound’ PSA to see whether the raised levels are caused by prostate cancer or benign disease. The probability of cancer is higher if the ‘free to total’ ratio is less than 20–25 per cent.

The rate of change of PSA (PSA velocity) can also be helpful in finding prostate cancer. In men with PSA above 4ng/ml, a velocity of greater than 0.75ng/ml/yr is thought to indicate a higher risk of cancer. This threshold may be lower in men with a PSA below 4ng/ml.

Monitoring cancer

After a diagnosis of cancer, regular PSA blood tests are also used to monitor the cancer activity in a man’s body. Generally, prostate cancer prompts higher and higher levels of blood-borne PSA as it grows. Regular blood tests can indicate whether the tumour is shrinking or enlarging and if the current treatment is working or not.

Where to get help

* Your doctor

* Urologist

* Cancer Council of Victoria, Information and Support Service Tel. 13 11 20

Things to remember

* A normal prostate gland secretes small amounts of a protein called prostate specific antigen (PSA) into the ejaculate and blood.

* Prostate cancer usually causes large amounts of PSA to enter the blood.

* The PSA blood test can detect prostate cancer at an early stage, before it causes symptoms and when it can be removed.

* An abnormal PSA test result can have a number of non-cancer causes. Other tests are needed to confirm the diagnosis.

* Prostate cancer testing and treatment is less likely to have a benefit in older men, particularly those over the age of 75 years.