Investigating CSI – Background material Table of Contents I ...

p30 Test
Unlike the presumptive acid phosphatase test, the detection of the p30 antigen
requires the presence of the protein without the need of the target to perform an
enzymatic function. This aids in the identification of semen in aged evidence
samples in which the acid phosphatase enzyme is functionally inactive. Prostate
specific antigen (PSA, also known as p30), is a glycoprotein produced by the
prostatic gland and secreted into seminal plasma (fluid). The p30 is secreted in
seminal fluid at concentrations of 200,000 to 5.5 million ng per mL. The
sensitivity of the p30 test is 4 ng/mL and therefore seminal fluid diluted up to 1 in
a million can also be detected. This means we can detect semen in samples that
have been rinsed or washed (without detergent). In addition, p30 protein is
produced from a larger protein that is degraded to release the p30 protein. Since
the p30 is a product of protein degradation it is readily detected in very old
samples and sample that have been stored in a plastic bags for a long periond.
The detection of the p30 antigen in forensic samples is often helpful because it
confirms the presence of semen even in samples that involve vasectomized or
azospermic individuals. The reported frequency of azoospermia of 1-9% in
seminal stains or swabs examined in sexual assault cases (1) can be expected
to rise, since the frequency of contraceptive vasectomy has been estimated to be
750 000 to 1,000 000 per year in the United States (2).
Source: http://www.dnatesting.biz/Semen_Sperm_ID/semen_sperm_id.html
23