Kits
FREE PSA
Kits
Description
Prostate cancer is the most frequent type of cancer found in
man and is the second cause of death due to cancer in
males. Until recently, digital rectal examination (DRE) was
frequently used as only diagnostic modality for the detection
of early stages of prostate cancer. In the recent years the
determination of serum PSA levels has become the most
accepted method to improve the diagnostic specificity of
DRE. Although PSA is a tissue specific protein and is not
solely tumor specific, it has become the most important
marker for prostate carcinoma, showing a better specificity
than other biochemical markers used in this context (PAP,
total alkaline phosphatase, carcinoembryonic antigen, etc.)
In 1979, Wang et al. isolated a specific antigen for normal
prostate tissue and called this protein PSA. PSA is a 33 kDa
serine proteinase. Immunohistological studies have shown
that PSA is localized in the cytoplasm of prostate acinar
cells, ductal epithelium and in the secretion on the ductal
lumina, present in normal, benign hyperplastic and
malignant prostate tissues as well metastatic prostate
cancer and in seminal plasma. If the structural integrity of
the prostate is disturbed and/or the gland size is increased,
the amount of PSA in the blood plasma may become
elevated. In the blood plasma, most of the PSA forms
complexes with various proteinase inhibitors. Only a small
fraction of PSA circulates as free inactive PSA. Basically
three major forms of PSA can be distinguished, only two of
which are immunoreactive. The predominant form of PSA is
a complex with α1-antichymotrypsin (ACT-PSA). Inactive
free PSA (f-PSA) represents around 10-40% of the
immunologically detectable PSA. The total amount of
immunoreactive PSA is known as total PSA (t-PSA). PSA
complexed with α- 2-macroglobulin cannot be detected by
immunological assays and is therefore frequently called
occult PSA (o-PSA).
Current methods of screening men for prostate cancer
utilize the detection of t-PSA. Levels of 4.0 ng/ml or higher
are strong indicators of the possibility of prostatic cancer
and are an indication for follow-up examinations of the
patient. However, elevated serum PSA levels are frequently
also attributed to benign prostatic hyperplasia, leading to a
high percentage of false positive screening results. A
potential solution to this problem involves the determination
of free PSA levels. Studies have suggested that the
percentage of free PSA is lower in patients with prostate
cancer than those with benign prostatic hyperplasia. Thus,
the measurement of free serum PSA in conjunction with
total PSA, can improve specificity of prostate cancer
screening in selected men with elevated total serum PSA
levels, which would subsequently reduce unnecessary
prostate biopsies with minimal effects on cancer detection
rates.
man and is the second cause of death due to cancer in
males. Until recently, digital rectal examination (DRE) was
frequently used as only diagnostic modality for the detection
of early stages of prostate cancer. In the recent years the
determination of serum PSA levels has become the most
accepted method to improve the diagnostic specificity of
DRE. Although PSA is a tissue specific protein and is not
solely tumor specific, it has become the most important
marker for prostate carcinoma, showing a better specificity
than other biochemical markers used in this context (PAP,
total alkaline phosphatase, carcinoembryonic antigen, etc.)
In 1979, Wang et al. isolated a specific antigen for normal
prostate tissue and called this protein PSA. PSA is a 33 kDa
serine proteinase. Immunohistological studies have shown
that PSA is localized in the cytoplasm of prostate acinar
cells, ductal epithelium and in the secretion on the ductal
lumina, present in normal, benign hyperplastic and
malignant prostate tissues as well metastatic prostate
cancer and in seminal plasma. If the structural integrity of
the prostate is disturbed and/or the gland size is increased,
the amount of PSA in the blood plasma may become
elevated. In the blood plasma, most of the PSA forms
complexes with various proteinase inhibitors. Only a small
fraction of PSA circulates as free inactive PSA. Basically
three major forms of PSA can be distinguished, only two of
which are immunoreactive. The predominant form of PSA is
a complex with α1-antichymotrypsin (ACT-PSA). Inactive
free PSA (f-PSA) represents around 10-40% of the
immunologically detectable PSA. The total amount of
immunoreactive PSA is known as total PSA (t-PSA). PSA
complexed with α- 2-macroglobulin cannot be detected by
immunological assays and is therefore frequently called
occult PSA (o-PSA).
Current methods of screening men for prostate cancer
utilize the detection of t-PSA. Levels of 4.0 ng/ml or higher
are strong indicators of the possibility of prostatic cancer
and are an indication for follow-up examinations of the
patient. However, elevated serum PSA levels are frequently
also attributed to benign prostatic hyperplasia, leading to a
high percentage of false positive screening results. A
potential solution to this problem involves the determination
of free PSA levels. Studies have suggested that the
percentage of free PSA is lower in patients with prostate
cancer than those with benign prostatic hyperplasia. Thus,
the measurement of free serum PSA in conjunction with
total PSA, can improve specificity of prostate cancer
screening in selected men with elevated total serum PSA
levels, which would subsequently reduce unnecessary
prostate biopsies with minimal effects on cancer detection
rates.