Prostate Specific Antigen (PSA)
Prostate specific antigen is a serine protease that
is produced by certain cells in the prostate gland
and serves to liquefy semen after ejaculation. It
plays a role in the diagnosis, treatment and
follow-up of patients with prostate cancer, but the
efficacy as an effective screening tool is under
evaluation and debate. The PSA level of 4.0ng/ml is
considered the upper limit of normal, but this
figure varies with age. And since the PSA is
indicative of the size of the prostate, increasing
PSA level may simply indicate enlarging prostate
tissue size.Measurement of PSA level
is the most sensitive test for early detection of
prostate cancer, it is elevated in about sixthly
five percent of cases of prostate cancers. But, it
is an imperfect tumor marker, because of a high
incidence of false negatives and lack of
specificity. While there may be elevated levels
of PSA level in prostate cancer, it is not diagnostic of
prostate cancer, because other conditions may cause
elevated levels. Such conditions include: benign
prostatic hyperplasia, prostatic infarction, prostattis, and conditions
requiring prolonged catheterization. Levels are also
higher in blacks. Combined use of seurum PSA levels
and digital rectal examination allows detection of a
significant percentage of prostate cancers while
they are still localized.
In patients that have established prostate cancers,
PSA measurements can be used to stage the disease,
assess response to treatment and detect early
relapse. But the effectiveness of isolated PSA
relapse is not known.
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