PSA testing and screening

What is the PSA test? 

Prostate-specific antigen, or PSA, is a protein produced by cells of the prostate gland. The PSA test measures the level of PSA in a man’s blood.

The blood level of PSA can be elevated for a number of reasons. The most important is prostate cancer but in addition a number of benign (non-cancerous) causes can raise the PSA. This includes a urinary tract infection, inflammation of the prostate or an enlarged prostate.

Is the PSA test recommended for prostate cancer screening?

PSA screening is where a blood PSA is obtained from a man who has no evidence of prostate cancer.  This allows us to calculate the risk of having the disease.

Recent evidence recommends PSA screening but there is widespread agreement that any man who is considering getting tested should first be informed in detail about the potential harms and benefits.

What is a normal PSA test result?

There is no specific normal or abnormal level of PSA but there is a strong correlation between raised PSA and prostate cancer.

We usually use a cut off level depending on your age. At Otago Urology we feel that the levels given below allow us to have a good safety margin to detect prosate cancer and not to over investigate a patient with a low risk.

These are: 

Age 50 -55                PSA above      3.5

Age 55-60                 PSA above      4.0

Age 60-65                 PSA above      4.5

Age 65-70                 PSA above      5.0

Age 70-75                 PSA above      5.5

              Age 75 +     PSA screening not recommended*

*Above the age of 75 we do not recommend routine screening as the risks of investigation and treatment outweigh the potential benefits.

It must be stated that there is no one PSA that can gaurentee prostate cancer and the disease can be present at any PSA  level. Factors that can increase the chance of prostate cancer despite a relatively low PSA include 

• A family history of prostate cancer (Father,Brother,or Uncle if diagnosed at less than 70y old)
• Being of Maori descent
• A rapid rise in serial PSA tests

 In general the higher a man’s PSA level, the more likely it is that he has prostate cancer.

 What if a screening test shows an elevated PSA level?

If a man who has no symptoms of prostate cancer chooses to undergo prostate cancer screening and is found to have an elevated PSA level, we usually recommend another PSA test to confirm the original finding and if your PSA is still above the threshold we would usually recommend a biopsy of your prostate.

During the biopsy multiple tiny samples of prostate tissue are collected by inserting thin needles into the prostate via the rectum/anus. This procedure is performed using local anaesthetic to numb the prostate and rectum and is under ultrasound guidance.  

A pathologist then examines the collected tissue under a microscope looking for any cancerous cells.

What are some of the limitations and potential harms of the PSA test for prostate cancer screening?

Finding a small tumor may not reduce a man’s chance of dying from prostate cancer. Some tumors found through PSA testing grow so slowly that they are unlikely to ever threaten a man’s life. Any treatment would be overdoing it and expose you to significant risk from complications of surgery or radiotherapy. 

A false-positive test result occurs when a man’s PSA level is elevated but no cancer is actually present. A false-positive test result may create anxiety for a man and his family and lead to additional medical procedures, such as a prostate biopsy, that can be harmful. Possible side effects of biopsies include serious infections, pain, and bleeding.

A false-negative test result occurs when a man’s PSA level is low even though he actually has prostate cancer. False-negative test results may give a man, his family, and his doctor false assurance that he does not have cancer, when he may in fact have a cancer that requires treatment.

How is the PSA test used in men who have been treated for prostate cancer?

The PSA test is used to monitor patients who have a history of prostate cancer to see if their cancer has recurred (come back).If a man’s PSA level begins to rise after prostate cancer treatment, it may be the first sign of a recurrence.

ANY DETECTABLE PSA IN A MAN WHO HAS HAD HIS PROSTATE REMOVED FOR CANCER IS ABNORMAL AND MUST BE FOLLOWED UP IMMEDIATELY