Page 1 - Prostate Specific Antigen (PSA)

Urological Health
Prostate specific antigen (PSA)
The prostate specific antigen is a blood test used by your physician to help assess your
prostate health.
he prostate is a gland wrapped around the male
Turethra, the urine channel between the bladder
and its control muscle, the urethral sphincter. Its main
function is to produce part of the semen ejaculated
at male orgasm. Each vas deferens carrying sperm
from the testicle connects to the prostate. The nerves
carried signals to produce erections run on either side
of the prostate.
bladder
prostate
urethra
What is Prostate specific antigen?
Prostate specific antigen (PSA) is an enzyme that
is produced by cells of the prostate gland and
contributes to the function of the semen. Under
normal circumstances, a small amount of this
substance is released from the prostate into the
blood stream. As a result, this can be easily measured
by means of an ordinary blood test. However, the
level can change depending on a variety of factors,
including the patient’s race, age, prostate size and
the presence of various diseases within the prostate.
Using PSA to detect or screen for
early prostate cancer
Over the last 2 decades, PSA has become an
invaluable tool to help diagnose patients with
prostate cancer and to follow their treatment results.
Originally, if the PSA value was greater than 4.0 ng/
mL, the patient would likely be investigated to rule
out cancer of the prostate. As researchers fine tuned
the test and its application to help diagnose prostate
cancer, PSA’s utility improved. The purpose was to
decrease the number of unnecessary investigations,
while still investigating appropriate patients. Ultimately,
this could lessen the over-diagnosis and over-treatment
of this common disease, whereas at the same time,
continue to diagnose significant disease burden.
How can PSA be made more helpful
in diagnosing prostate cancer?
Several modifications, which include changing the
cut off values according to patient’s age, i.e. age-
specific PSA levels were used. Instead of an absolute
value of 4.0 ng/mL as being suspicious of prostate
cancer for all men, different PSA values could be used
for different aged men. For example, a level of 2.5
ng/mL, in a younger man could be the threshold for
investigating. Whereas, a gentleman in his seventh
decade may have a threshold level of 6.5 ng/mL for
investigations.
As well, the change in the absolute value over time
may increase the accuracy of the test in diagnosing
prostate cancer. This is known as the PSA velocity. If
the patient’s PSA value increases too quickly over a
given period of time, this could increase the suspicion
of prostate cancer. If infection or another non-
cancerous cause of rapid rate of change in the PSA is
not present, the physician may institute further testing.
Another way to increase the accuracy of PSA in
screening men for prostate cancer is the free/total
ratio of PSA. The free/total PSA ratio is calculated
based on the amount of PSA that is bound to proteins
in the blood stream. A lower free/total PSA ratio will
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