Prostate Cancer Screening

The Prostate PSA Test

PSA is an abbreviation for Prostate Specific Antigen. The amount of PSA in the blood is an essential parameter for detecting and monitoring prostate ailments.

A specific protein

PSA is a protein produced by the prostate gland and which is found in the blood. It is specific to the prostate. i.e. it is not produced by any other organ. Thus it is only present in men.

The PSA protein is absorbed in the blood so it isn’t necessary to have an empty stomach before the test can take place.

PSA is not toxic to the body and possesses no danger in itself. At the age of 50 and over, to have a slightly increased PSA level without other symptoms, is neither worrying nor does it require treatment. In this way, the PSA level might be compared to the cholesterol level. The level of PSA is simply an indicator that, when elevated, suggests that a visit to a urologist is recommended.

How to interpret the PSA level

The normal level of PSA depends upon the method of measurement: but typically it should be less than 2.5 to 4 ng/ml (nanogrammes per millilitre). This level increases spontaneously with age and also has a relationship with the volume of the prostate. However, be aware that a PSA level equal to or less than 4 ng/ml doesn’t necessarily indicate a prostate without problems any more than a slightly increased PSA of 4 to 10 ng/ml indicates that the prostate is cancerous.

PSA is specific to the prostate and not to any particular prostate malady.

For a correct interpretation it is necessary to consider the PSA level in conjunction with the Digital Rectal Exam (DRE) and an ultrasound scan. The urologist must take account of all three results before arriving at a conclusion.

In the even of a high PSA level, disproportionate to the volume of the prostate, a biopsy might be necessary. Note that one gramme of cancerous prostate cells secrets 10 times more PSA than one gramme of prostatic adenoma.

What can increase the PSA level?

• prostatitis
• prostatic adenoma
• prostate cancer
• urinary infection
• acute urine retention
• the Digital Rectal Exam
• a prostate biopsy

Prostatic Adenoma or Cancer?

To aid the urologist in their diagnosis, some other parameters are of interest:

• PSA velocity : the change in PSA level during a period of time. PSA is measured at regular intervals, every 3 or 6 months. The testing should always be carried out by the same laboratory to obtain comparable results. If the PSA level increases with each new test, it might be cancer. In this case a biopsy is necessary.

• PSA density : the level of PSA with respect to the prostate volume as determined by endorectal ultrasound. A theoretical density existsabove which there is a risk of cancer. However the use of this method must be evaluated on a case by case basis.

The measure of free PSA

The level of PSA looked at up to now has been the total PSA. However we know that there exists in the blood a free PSA (part of the total PSA not associated with protein).

When cancer is present, the amount of free PSA is less than in the case of prostatic adenoma. Thus it is useful to calculate the ratio of free PSA to total PSA. If the value is less than 20% (or 15% depending upon the laboratory doing the analysis), this indicates a risk of cancer. In such an eventuality, the urologist will doubtless request a biopsy.

See also: Prostate DRE - PSA ultrasound exam