I don't know what the difference between these two are, but I suspect
they are both measures of the total density of PSA in the blood.  This
is measured in nanograms per milliliter.  A high value may be an
indication of prostate cancer and suggests that further measures such as
a biopsy may be appropriate.     What is considered high PSA is still
evolving and it depends in part on age.   A value over 4 ng/ml was the
previous value, but now some doctors suggest that anything over 2.5
ng/ml, particularly for younger men, is a warning sign.   This is
complicated by the fact that a common condition in older men,  BPH, may
produce ongoing fairly high values. (Prostatitis can also increase PSA,
but that may be temporary.)  If you have a high value, it is up to your
doctor to decide what to do based on your individual situation.

There are two different kinds of PSA.  One is called free and one is
called bound.   If the percentage of free PSA out of the total value is
too low, that makes prostate cancer more likely.  A higher value is more
consistent with BPH.  There is no hard fast rule about what is low, but
often a figure of 16 percent is chosen as the borderline.  The main
purpose of the free PSA test is to distinguish those cases where a
biopsy is warranted from those where it isn't.

Just which tests are used is a matter for your doctor to decide.  He may
decide to do a biopsy based just on the total PSA value, in which case a
free PSA test would be redundant.   If the biopsy shows cancer, that is
pretty definite.  On the other hand, in a relatively small number of
cases, the biopsy may miss a small cancer that is present.  So if the
doctor still suspects cancer,  he may recommend a repeat biopsy at a
later time.  In that case,  free PSA tests may help decide if additional
biopsies are necessary.

There are also other criteria which doctors use in deciding whether or
not to do a biopsy.  One is the rate at which the PSA increases.  If
this is high, that makes cancer more likely.

Some cancers don't produce unusual PSA readings.  That is why doctors
also do a digital rectal exam to feel the prostate and see if there are
any abnormalities.

i know of no psas.   are you sure it's not PSA's  as in public service
announcements.

~ curtis

knowledge is power - growing old is mandatory - growing wise is optional    
"Many more men die with prostate cancer than of it. Growing old is
invariably fatal. Prostate cancer is only sometimes so."